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Fabrication of three-dimensional GaAs–AlGaAS heterostructures for improving carrier injection efficiency in quantum-wire FETs
ARTICLE IN PRESS
Physica E 40 (2007) 328–331 www.elsevier.com/locate/physe
Fabrication of three-dimensional GaAs–AlGaAS heterostructures for improving carrier injection efficiency in quantum-wire FETs Y.J. Kima,b, Y.J. Seoa, E.H. Kima, D.H. Kima, C.H. Rohb, H. Kimb, C.K. Hahnb, Y.M. Sungc, M. Ogurad, T.G. Kima, a
Department of Electronic Engineering, Korea University, Seoul 136-701, South Korea Nano-scale Quantum Devices Research Center, KETI, Gyeonggi 463-816, South Korea c Department of Materials Science Engineering, Korea University, Seoul 136-701, South Korea d Photonics Research Institute, Tsukuba 2nd Center, AIST, Japan b
Available online 29 June 2007
Abstract Three-dimensional (3D) GaAs–AlGaAS heterostructures were grown by selective-area molecular beam epitaxy on a patterned GaAs(0 0 1) substrate to improve the efficiency of carrier transport from the source to the drain through 1D channels in quantum-wire (QWR) field-effect transistors. Prior to the QWR growth, GaAs ridge structures with 2 mm line-and-space patterns, were prepared as the starting materials. The surface of the ridge was chemically treated with an NH3 solution to improve the surface roughness and thereby to minimize the defect density at the GaAs/AlGaAs interface. Then, GaAs/AlGaAs QWRs were grown on top of the ridge structures with optimum growth conditions. A scanning electron microscope and position-resolved m-PL measurements along the QWR direction showed that 3D GaAs–AlGaAS heterostructures, where 1D QWRs were adiabatically coupled with a 2D electron gas, were successfully fabricated. r 2007 Elsevier B.V. All rights reserved. PACS: 68.65.La; 81.07.Lk; 74.78.Fk; 81.15.Hi Keywords: GaAs–AlGaAS; Quantum wire; FETs; Heterostructures; Selective area MBE
1. Introduction Because of the advantages arising from one-dimensional (1D) electronic systems [1–3], many efforts have been made to fabricate high-quality semiconductor quantum-wire (QWR) structures as well as to apply such 1D structures to various electrical and optical devices [4–9]. The QWR field-effect transistor (FET), where the carrier mobility would be extremely enhanced because of the reduced electron scattering in a 1D electronic channel, is one of the good examples that have been developed over the past decade. The universal conductance (g0 ¼ 2e2/h) fluctuation, known to be observed only in an ideal conductor, is one of the unique features of an ideal QWR FET [10]. However, these electron transmission properties as an ideal conCorresponding author. Tel.: +82 2 3290 3255; fax: +82 2 924 5119.
E-mail address: [email protected] (T.G. Kim). 1386-9477/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.physe.2007.06.052
ductor have been often observed in the form of fractional conductance (0.x g0) or resonance [11,12] due to the nonideality of QWR FETs and the incomplete ohmic contacts. Many research groups have focused on making defect-free QWRs. However, we need to make an ideal ohmic contact to the source/drain (S/D) region of the QWR to observe these inherent properties of 1D carrier transport in QWR FETs. This ideal ohmic contact can be realized by forming an adiabatic funnel structure [12]. The adiabaticity of the dimensional changeover avoids reflections at the entrance to the wire and thus ensures the filling of all the outgoing states [13]. For traditional semiconductor QWR systems [14–18], the energy level difference between the 2D electron gas (2DEG) S/D and 1D QWR channel is abrupt (or nonadiabatic) as depicted in Fig. 1(a). This abrupt behavior results in carrier scattering (or reflection) at the interface between the S/D and QWR channel since the momentum and/or reflection is different in each region, decreasing
ARTICLE IN PRESS Y.J. Kim et al. / Physica E 40 (2007) 328–331
Fig. 1. Conceptual drawings of the: (a) conventional and (b) proposed 2DEG–1DEG system.
overall channel conductance. To solve the problem, we proposed an adiabatic 3D quantum funnel structure in which the energy levels were gradually changed from the 2DEG S/D region to a 1D electron channel as shown in Fig. 1(b). In this work, high-quality 3D heterostructures, where the carriers can gradually transport from the 2DEG S/D electrodes to the 1D electron channel with reduced scattering, were successfully fabricated by selective area molecular bean epitaxy (SA-MBE) [19–24] on patterned GaAs substrates and confirmed by scanning electron microscope (SEM) and micro-photoluminescence (m-PL). 2. Experiment To fabricate adiabatic 3D quantum funnel structures, shown in Fig. 1(b), SA-MBE was performed on 2 mm lineand-space patterns. The details on the pattern design and sample preparation are described in Ref. [25]. The growth parameters such as group-V sources (As2, As4), V/III ratio, growth temperature, substrate orientation and rotation speed were calibrated with a test layer structure to find the optimum growth condition before growing the QWR FET structure. The test layer consisted of a 200 nm thick GaAs buffer layer, 10 periods of Al(Ga)As/GaAs layers with a thickness of 100 and 5 nm, respectively, and a 10 nm thick GaAs cap layer. The growth temperature and the group-V source during the growth of Al(Ga)As/GaAs layers were changed from 500 to 650 1C and from As2 to As4. Finally, we found that two growth modes could be developed depending on the growth temperature and the V/III ratio. Figs. 2(a) and (b) show the SEM cross-sections of the test layers grown on patterned substrates in the patternwidth maintaining and in the pattern-width varying growth mode. Under relatively lower growth temperatures (o550 1C) and higher V/III ratios (50) using As4 cracked dimer sources, we found that the original pattern width of 2 mm was maintained since the surface migration of the
329
Fig. 2. SEM cross-sections of the test layers grown by SA-MBE on patterned substrates: (a) in the pattern-width maintaining and (b) in the pattern-width varying mode.
group-III adatom was extremely suppressed (see Fig. 2(a)). On the other hand, since the surface migration of the group-III adatom was extremely enhanced under relatively higher growth temperatures (4610 1C) and lower V/III ratios (less than 10, using tetramer arsenic), new facets, such as the {3 1 1}A plane, with a high surface energy, began to generate. They took up the width of the (1 0 0) plane as the thickness of the AlGaAs layer increased, eventually leaving the {3 1 1}A plane at the end of the growth, as shown in Fig. 2(b). For the 3D quantum funnel structure growth, conventional high electron mobility transistor structure with AlGaAs spacer layer thickness of 10 nm and the AlGaAs donor layer of 50 nm was employed. The 2DEG concentration and mobility on the reference planner substrate were measured to 4.4 1011 cm2 and 0.15 106 cm2/V s at 77 K, respectively. The final width of the QWR for the 3D quantum funnel structure was set to 60 nm by adjusting the AlGaAs barrier thickness. 3. Results and discussion Based on these experiments, we fabricated a 3D ridgetype QWR FET structure by using pattern-width varying mode, described in Fig. 2(b), on the GaAs substrate patterned with a 2 2 mm line and space along the [0 1 1] direction. The growth temperature was 640 1C and the V/III ratio was 10. A 10 nm thick GaAs buffer and a 500 nm thick Al0.28Ga0.72As barrier layer were grown to construct a sharp reverse-V shape with the clean surface. A 9 nm thick GaAs layer, a 100 nm thick Al0.28Ga0.72As upper barriers and a 10 nm GaAs capping layer were sequentially grown on it. Fig. 3(a) shows the cross-sectional SEM image of the QWR structure grown on the stripe patterns with a thin GaAs cap layer. In this figure, the surface of the valley appeared to be rougher than that of the other region. We thought this to be the result of the over-rich Ga atoms that migrated partially from the
ARTICLE IN PRESS 330
Y.J. Kim et al. / Physica E 40 (2007) 328–331
Fig. 4. Position-resolved m-PL spectra measured along the QWR.
Fig. 3. (a) SEM cross-sections after QWR growth on a line-and-stripe pattern and (b) SEM top image in the cross-over region of the 2D-1DEG QWR channel.
{1 1 1}A plane. The rough surface of the {1 1 1}A side wall, especially the region shaded in Fig. 3(a), may have resulted from the lack of arsenic flux under no substrate rotation, during the growth. On the other hand, as the thickness of the AlGaAs layer increased, new facets such as the {3 1 1}A plane were generated at the top of the ridge and the width of the (1 0 0) plane was reduced, as mentioned earlier. However, for the practical 3D QWR structure, the surface of the {1 1 1}A side wall became very smooth because there was no source, such as {1 1 1}A side wall, which was able to supply extra Ga atoms as shown in Fig. 3(b). Fig. 3(b) shows the top SEM image of the 3D QWR structure grown on the stripe patterns with a thin GaAs cap layer. The quantum-size effect caused by the modulation of the QWR width was investigated by scanning m-PL measurements whose spatial resolution and scanning steps were 700 and 100 nm, respectively. Fig. 4(a) shows the m-PL spectra measured along the QWRs with a modified 3D ridge structure. Each of the PL signals corresponded to the position of the QWR indicated by the arrows on the SEM image of Fig. 4. PL signals from the GaAs quantum structures were resolved near the wavelength of 780 nm along the dotted line. Many signals, observed in the wavelengths between 690 and 720 nm, are thought to come from the unexpected quantum structures formed by step bunching around the side walls. It is very interesting that emission wavelengths from the 2DEG, indicated as a dotted arrow, showed monotonic blue-shifts as the
measurement points moved from one of the ends to the center of the 3D structure. We consider this shift to be caused by the quantum confining effect of the 2DEG. That is, additional quantum confinement effect of the 2DEG in the lateral direction resulted in a formation of a quasi-1D structure at the center. The energy level shift caused by the additional quantum confinement effect was estimated to be 20 meV for the corresponding structure. This effect is not very large at this moment, but good enough to verify the feasibility of the idea proposed in the experiment and expected to serve in realizing high-performance quantumwire devices.
4. Conclusion High-quality 3D heterostructures were constructed by SA-MBE using a specially patterned GaAs (0 0 1) substrate. During the growth, we found two different growth modes: one was the mode for maintaining the pattern width and the other was the mode for generating new facets during the growth. We then fabricated 3D QWR FET heterostructures by combining these two growth modes. Finally, the formation of the 3D heterostructure was confirmed by both SEM and m-PL. Blue-shifts along the QWR observed in the m-PL spectra, which occurred due to the quantum-size effect resulted from the modulation of the QWR width, verified that adiabatically coupled 3D quantum heterostructure was successfully realized.
Acknowledgments This work was supported by the Korea Research Foundation grant funded by Korean Government (MOEHRD) (KRF-2005-041-D00478) and the MOST/ KOSEF through Quantum Photonic Science Research Center, Korea.
ARTICLE IN PRESS Y.J. Kim et al. / Physica E 40 (2007) 328–331
References [1] T. Sugaya, K.Y. Jang, C.K. Hahn, M. Ogura, K. Komori, A. Shinoda, K. Yonei, J. Appl. Phys. 97 (2005) 034507. [2] Y. Xia, P. Yang, Y. Wu, B. Mayers, B. Gates, Y. Yin, F. Kim, H. Yan, Adv. Mater. 15 (2003) 353. [3] J. Goldberger, R. He, Y. Zhang, S.K. Lee, H. Yan, H.J. Choi, P. Yang, Nature 422 (2003) 599. [4] Y. Higuchi, S. Osaki, T. Kitada, S. Shimomura, Y. Takasuka, K. Komori, M. Ogura, S. Hiyamizu, Semiconductor Device Research Symposium, 2005. [5] F. Capasso, E. Heidelberg, Phys. Quantum Electron Devices 28 (1990) 367. [6] F. Schrenk, C. Pflugl, M. Austerer, S. Golka, G. Strasser, R.P. Green, L.R. Wilson, D.G. Revin, E.A. Zibik, J.W. Cockburn, C.M. Tey, A.B. Krysa, J.S. Roberts, A.G. Cullis, Lasers Electro-Optics (CLEO) 1 (2005) 257. [7] M. Yumoto, S. Kasai, H. Hasegawa, Compd. Semicond. 2004, Proc. Inst. Phys. Conf. 184 (2005) 21. [8] H. Hasegawa, T. Sato, Electrochim. Acta 50 (2005) 3015. [9] A.M. Hashim, S. Kasai, T. Hashizume, H. Hasegawa, Jpn. J. Appl. Phys. 44 (2005) 2729. [10] R. Landauer, IBN J. Res. Dev. (32) 306.
331
[11] E. Tekman, S. Ciraci, Phys. Rev. B 43 (1991) 7145. [12] R. De Picciotto, H.L. Stormer, A. Yacoby, L.N. Pfeiffer, K.W. Baldwin, K.W. West, Phys. Rev. Lett. 85 (2000) 1730. [13] L.I. Glazman, JETP Lett. 48 (1988) 238. [14] K. Komori, et al., IEEE J. Quantum Electron. 28 (1992) 1894. [15] D.H. Marti, M.A. Dupertuis, B. Deveaud, Quantum Electron. 41 (2005) 848. [16] K. Shimomura, et al., IEEE J. Quantum Electron. 2 (1992) 478. [17] C. Jiang, T. Muranaka, H. Hasegawa, Jpn. J. Appl. Phys. 40 (2001) 3003. [18] K.Y. Jang, T. Sugaya, C.K. Hahn, M. Ogura, K. Komori, Appl. Phys. Lett. 83 (2003) 701. [19] C.K. Hahn, T. Sugaya, K.Y. Jang, K.L. Wang, M. Ogura, Jpn. J. Appl. Phys. 42 (2003) 2399. [20] A.Y. Cho, J. Appl. Phys. 46 (1975) 783. [21] G.M. Metze, H.M. Levy, D.W. Woodard, C.E. Wood, L.F. Eastman, Appl. Phys. Lett. 37 (1980) 628. [22] T. Yao, T. Minato, S. Mackawa, J. Appl. Phys. 53 (1982) 4236. [23] P.N. Favennec, L. Henry, A. Regreny, M. Salvi, Electron. Lett. 18 (1982) 933. [24] A.Z. Li, H. Cheng, A.G. Milnes, J. Electrochem. Soc. 130 (1982) 2072. [25] C.K. Hahn, C.H. Roh, H. Kim, J. Kor. Phys. Soc. 45 (2004) 799.
Physica E 40 (2007) 328–331 www.elsevier.com/locate/physe
Fabrication of three-dimensional GaAs–AlGaAS heterostructures for improving carrier injection efficiency in quantum-wire FETs Y.J. Kima,b, Y.J. Seoa, E.H. Kima, D.H. Kima, C.H. Rohb, H. Kimb, C.K. Hahnb, Y.M. Sungc, M. Ogurad, T.G. Kima, a
Department of Electronic Engineering, Korea University, Seoul 136-701, South Korea Nano-scale Quantum Devices Research Center, KETI, Gyeonggi 463-816, South Korea c Department of Materials Science Engineering, Korea University, Seoul 136-701, South Korea d Photonics Research Institute, Tsukuba 2nd Center, AIST, Japan b
Available online 29 June 2007
Abstract Three-dimensional (3D) GaAs–AlGaAS heterostructures were grown by selective-area molecular beam epitaxy on a patterned GaAs(0 0 1) substrate to improve the efficiency of carrier transport from the source to the drain through 1D channels in quantum-wire (QWR) field-effect transistors. Prior to the QWR growth, GaAs ridge structures with 2 mm line-and-space patterns, were prepared as the starting materials. The surface of the ridge was chemically treated with an NH3 solution to improve the surface roughness and thereby to minimize the defect density at the GaAs/AlGaAs interface. Then, GaAs/AlGaAs QWRs were grown on top of the ridge structures with optimum growth conditions. A scanning electron microscope and position-resolved m-PL measurements along the QWR direction showed that 3D GaAs–AlGaAS heterostructures, where 1D QWRs were adiabatically coupled with a 2D electron gas, were successfully fabricated. r 2007 Elsevier B.V. All rights reserved. PACS: 68.65.La; 81.07.Lk; 74.78.Fk; 81.15.Hi Keywords: GaAs–AlGaAS; Quantum wire; FETs; Heterostructures; Selective area MBE
1. Introduction Because of the advantages arising from one-dimensional (1D) electronic systems [1–3], many efforts have been made to fabricate high-quality semiconductor quantum-wire (QWR) structures as well as to apply such 1D structures to various electrical and optical devices [4–9]. The QWR field-effect transistor (FET), where the carrier mobility would be extremely enhanced because of the reduced electron scattering in a 1D electronic channel, is one of the good examples that have been developed over the past decade. The universal conductance (g0 ¼ 2e2/h) fluctuation, known to be observed only in an ideal conductor, is one of the unique features of an ideal QWR FET [10]. However, these electron transmission properties as an ideal conCorresponding author. Tel.: +82 2 3290 3255; fax: +82 2 924 5119.
E-mail address: [email protected] (T.G. Kim). 1386-9477/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.physe.2007.06.052
ductor have been often observed in the form of fractional conductance (0.x g0) or resonance [11,12] due to the nonideality of QWR FETs and the incomplete ohmic contacts. Many research groups have focused on making defect-free QWRs. However, we need to make an ideal ohmic contact to the source/drain (S/D) region of the QWR to observe these inherent properties of 1D carrier transport in QWR FETs. This ideal ohmic contact can be realized by forming an adiabatic funnel structure [12]. The adiabaticity of the dimensional changeover avoids reflections at the entrance to the wire and thus ensures the filling of all the outgoing states [13]. For traditional semiconductor QWR systems [14–18], the energy level difference between the 2D electron gas (2DEG) S/D and 1D QWR channel is abrupt (or nonadiabatic) as depicted in Fig. 1(a). This abrupt behavior results in carrier scattering (or reflection) at the interface between the S/D and QWR channel since the momentum and/or reflection is different in each region, decreasing
ARTICLE IN PRESS Y.J. Kim et al. / Physica E 40 (2007) 328–331
Fig. 1. Conceptual drawings of the: (a) conventional and (b) proposed 2DEG–1DEG system.
overall channel conductance. To solve the problem, we proposed an adiabatic 3D quantum funnel structure in which the energy levels were gradually changed from the 2DEG S/D region to a 1D electron channel as shown in Fig. 1(b). In this work, high-quality 3D heterostructures, where the carriers can gradually transport from the 2DEG S/D electrodes to the 1D electron channel with reduced scattering, were successfully fabricated by selective area molecular bean epitaxy (SA-MBE) [19–24] on patterned GaAs substrates and confirmed by scanning electron microscope (SEM) and micro-photoluminescence (m-PL). 2. Experiment To fabricate adiabatic 3D quantum funnel structures, shown in Fig. 1(b), SA-MBE was performed on 2 mm lineand-space patterns. The details on the pattern design and sample preparation are described in Ref. [25]. The growth parameters such as group-V sources (As2, As4), V/III ratio, growth temperature, substrate orientation and rotation speed were calibrated with a test layer structure to find the optimum growth condition before growing the QWR FET structure. The test layer consisted of a 200 nm thick GaAs buffer layer, 10 periods of Al(Ga)As/GaAs layers with a thickness of 100 and 5 nm, respectively, and a 10 nm thick GaAs cap layer. The growth temperature and the group-V source during the growth of Al(Ga)As/GaAs layers were changed from 500 to 650 1C and from As2 to As4. Finally, we found that two growth modes could be developed depending on the growth temperature and the V/III ratio. Figs. 2(a) and (b) show the SEM cross-sections of the test layers grown on patterned substrates in the patternwidth maintaining and in the pattern-width varying growth mode. Under relatively lower growth temperatures (o550 1C) and higher V/III ratios (50) using As4 cracked dimer sources, we found that the original pattern width of 2 mm was maintained since the surface migration of the
329
Fig. 2. SEM cross-sections of the test layers grown by SA-MBE on patterned substrates: (a) in the pattern-width maintaining and (b) in the pattern-width varying mode.
group-III adatom was extremely suppressed (see Fig. 2(a)). On the other hand, since the surface migration of the group-III adatom was extremely enhanced under relatively higher growth temperatures (4610 1C) and lower V/III ratios (less than 10, using tetramer arsenic), new facets, such as the {3 1 1}A plane, with a high surface energy, began to generate. They took up the width of the (1 0 0) plane as the thickness of the AlGaAs layer increased, eventually leaving the {3 1 1}A plane at the end of the growth, as shown in Fig. 2(b). For the 3D quantum funnel structure growth, conventional high electron mobility transistor structure with AlGaAs spacer layer thickness of 10 nm and the AlGaAs donor layer of 50 nm was employed. The 2DEG concentration and mobility on the reference planner substrate were measured to 4.4 1011 cm2 and 0.15 106 cm2/V s at 77 K, respectively. The final width of the QWR for the 3D quantum funnel structure was set to 60 nm by adjusting the AlGaAs barrier thickness. 3. Results and discussion Based on these experiments, we fabricated a 3D ridgetype QWR FET structure by using pattern-width varying mode, described in Fig. 2(b), on the GaAs substrate patterned with a 2 2 mm line and space along the [0 1 1] direction. The growth temperature was 640 1C and the V/III ratio was 10. A 10 nm thick GaAs buffer and a 500 nm thick Al0.28Ga0.72As barrier layer were grown to construct a sharp reverse-V shape with the clean surface. A 9 nm thick GaAs layer, a 100 nm thick Al0.28Ga0.72As upper barriers and a 10 nm GaAs capping layer were sequentially grown on it. Fig. 3(a) shows the cross-sectional SEM image of the QWR structure grown on the stripe patterns with a thin GaAs cap layer. In this figure, the surface of the valley appeared to be rougher than that of the other region. We thought this to be the result of the over-rich Ga atoms that migrated partially from the
ARTICLE IN PRESS 330
Y.J. Kim et al. / Physica E 40 (2007) 328–331
Fig. 4. Position-resolved m-PL spectra measured along the QWR.
Fig. 3. (a) SEM cross-sections after QWR growth on a line-and-stripe pattern and (b) SEM top image in the cross-over region of the 2D-1DEG QWR channel.
{1 1 1}A plane. The rough surface of the {1 1 1}A side wall, especially the region shaded in Fig. 3(a), may have resulted from the lack of arsenic flux under no substrate rotation, during the growth. On the other hand, as the thickness of the AlGaAs layer increased, new facets such as the {3 1 1}A plane were generated at the top of the ridge and the width of the (1 0 0) plane was reduced, as mentioned earlier. However, for the practical 3D QWR structure, the surface of the {1 1 1}A side wall became very smooth because there was no source, such as {1 1 1}A side wall, which was able to supply extra Ga atoms as shown in Fig. 3(b). Fig. 3(b) shows the top SEM image of the 3D QWR structure grown on the stripe patterns with a thin GaAs cap layer. The quantum-size effect caused by the modulation of the QWR width was investigated by scanning m-PL measurements whose spatial resolution and scanning steps were 700 and 100 nm, respectively. Fig. 4(a) shows the m-PL spectra measured along the QWRs with a modified 3D ridge structure. Each of the PL signals corresponded to the position of the QWR indicated by the arrows on the SEM image of Fig. 4. PL signals from the GaAs quantum structures were resolved near the wavelength of 780 nm along the dotted line. Many signals, observed in the wavelengths between 690 and 720 nm, are thought to come from the unexpected quantum structures formed by step bunching around the side walls. It is very interesting that emission wavelengths from the 2DEG, indicated as a dotted arrow, showed monotonic blue-shifts as the
measurement points moved from one of the ends to the center of the 3D structure. We consider this shift to be caused by the quantum confining effect of the 2DEG. That is, additional quantum confinement effect of the 2DEG in the lateral direction resulted in a formation of a quasi-1D structure at the center. The energy level shift caused by the additional quantum confinement effect was estimated to be 20 meV for the corresponding structure. This effect is not very large at this moment, but good enough to verify the feasibility of the idea proposed in the experiment and expected to serve in realizing high-performance quantumwire devices.
4. Conclusion High-quality 3D heterostructures were constructed by SA-MBE using a specially patterned GaAs (0 0 1) substrate. During the growth, we found two different growth modes: one was the mode for maintaining the pattern width and the other was the mode for generating new facets during the growth. We then fabricated 3D QWR FET heterostructures by combining these two growth modes. Finally, the formation of the 3D heterostructure was confirmed by both SEM and m-PL. Blue-shifts along the QWR observed in the m-PL spectra, which occurred due to the quantum-size effect resulted from the modulation of the QWR width, verified that adiabatically coupled 3D quantum heterostructure was successfully realized.
Acknowledgments This work was supported by the Korea Research Foundation grant funded by Korean Government (MOEHRD) (KRF-2005-041-D00478) and the MOST/ KOSEF through Quantum Photonic Science Research Center, Korea.
ARTICLE IN PRESS Y.J. Kim et al. / Physica E 40 (2007) 328–331
References [1] T. Sugaya, K.Y. Jang, C.K. Hahn, M. Ogura, K. Komori, A. Shinoda, K. Yonei, J. Appl. Phys. 97 (2005) 034507. [2] Y. Xia, P. Yang, Y. Wu, B. Mayers, B. Gates, Y. Yin, F. Kim, H. Yan, Adv. Mater. 15 (2003) 353. [3] J. Goldberger, R. He, Y. Zhang, S.K. Lee, H. Yan, H.J. Choi, P. Yang, Nature 422 (2003) 599. [4] Y. Higuchi, S. Osaki, T. Kitada, S. Shimomura, Y. Takasuka, K. Komori, M. Ogura, S. Hiyamizu, Semiconductor Device Research Symposium, 2005. [5] F. Capasso, E. Heidelberg, Phys. Quantum Electron Devices 28 (1990) 367. [6] F. Schrenk, C. Pflugl, M. Austerer, S. Golka, G. Strasser, R.P. Green, L.R. Wilson, D.G. Revin, E.A. Zibik, J.W. Cockburn, C.M. Tey, A.B. Krysa, J.S. Roberts, A.G. Cullis, Lasers Electro-Optics (CLEO) 1 (2005) 257. [7] M. Yumoto, S. Kasai, H. Hasegawa, Compd. Semicond. 2004, Proc. Inst. Phys. Conf. 184 (2005) 21. [8] H. Hasegawa, T. Sato, Electrochim. Acta 50 (2005) 3015. [9] A.M. Hashim, S. Kasai, T. Hashizume, H. Hasegawa, Jpn. J. Appl. Phys. 44 (2005) 2729. [10] R. Landauer, IBN J. Res. Dev. (32) 306.
331
[11] E. Tekman, S. Ciraci, Phys. Rev. B 43 (1991) 7145. [12] R. De Picciotto, H.L. Stormer, A. Yacoby, L.N. Pfeiffer, K.W. Baldwin, K.W. West, Phys. Rev. Lett. 85 (2000) 1730. [13] L.I. Glazman, JETP Lett. 48 (1988) 238. [14] K. Komori, et al., IEEE J. Quantum Electron. 28 (1992) 1894. [15] D.H. Marti, M.A. Dupertuis, B. Deveaud, Quantum Electron. 41 (2005) 848. [16] K. Shimomura, et al., IEEE J. Quantum Electron. 2 (1992) 478. [17] C. Jiang, T. Muranaka, H. Hasegawa, Jpn. J. Appl. Phys. 40 (2001) 3003. [18] K.Y. Jang, T. Sugaya, C.K. Hahn, M. Ogura, K. Komori, Appl. Phys. Lett. 83 (2003) 701. [19] C.K. Hahn, T. Sugaya, K.Y. Jang, K.L. Wang, M. Ogura, Jpn. J. Appl. Phys. 42 (2003) 2399. [20] A.Y. Cho, J. Appl. Phys. 46 (1975) 783. [21] G.M. Metze, H.M. Levy, D.W. Woodard, C.E. Wood, L.F. Eastman, Appl. Phys. Lett. 37 (1980) 628. [22] T. Yao, T. Minato, S. Mackawa, J. Appl. Phys. 53 (1982) 4236. [23] P.N. Favennec, L. Henry, A. Regreny, M. Salvi, Electron. Lett. 18 (1982) 933. [24] A.Z. Li, H. Cheng, A.G. Milnes, J. Electrochem. Soc. 130 (1982) 2072. [25] C.K. Hahn, C.H. Roh, H. Kim, J. Kor. Phys. Soc. 45 (2004) 799.