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4212. Plasma anodization of GaAs in a dc discharge. (USA)
Classified abstracts 4211-4215 surface mobility during deposition when the substrate is held at room temperature. Pinholes formed in the ZnPc were filled with the metal and formed shorts between the two metal layers. This phenomenon is explained and interpreted. W Katz et al, J Fac Sci Technol, 15 (4), 1978, 1561-1564. 36 4211. Alloy compositional profiles by AES, ESCA and ion sputtering: air-exposed Fe~-xPdx films. (USA) Surface studies of air-exposed, 1000 A, thick Fel-xPd., alloy films with x = 0.06-4).74 were carried out using AES, ESCA and in situ ion sputtering techniques. It was found that Fe is preferentially oxidized on the surface with a Pd-enriched region formed underneath the oxide layer. The iron oxide thickness decreases linearly as the Pd concentration is increased, becoming quite small for x > 0.6. Fe203 is the dominant oxidation product for the lower Pd concentration alloys while Fe30., appears to be the major oxide for x > 0.36. The steady state composition of the surfaces measured both by AES and ESCA techniques after prolonged sputtering also indicated that the relative Pd-to-Fe sputtering yield remains constant for films with x between 0.06 and ~0.38 and decreases to another constant value for films with larger x values. No preferential sputtering is observed in the AES case for alloys with x > 0.38, if the atomic density is taken into account; for x < 0.38, Pd sputters about twice as fast as Fe. In the ESCA case, very strong preferential sputtering of Pd to Fe is observed. Possible origins for this sputtering yield change, including the phase transition and the residual oxygen content of the alloy, are discussed. Wen-Yaung Lee et al, J Vac Sci Technol, 15 (4), 1978, 1549-1553. 36 4212. Plasma anodization of GaAs in a dc discharge. (USA) Thin oxide films have been grown by anodization of GaAs in the negative glow region of a dc oxygen discharge. As-grown and annealed films grown on both p- and n-type bulk GaAs were characterized by conventional electrical measurements and by Auger analysis. The anodic oxide displayed ohmic characteristics up to fields of 0.5 ,"<. 106 V cm - t with a resistivity of 101"~cm in the as-grown condition and over l0 ts ~~cm after anneal. Capacitance-voltage measurements indicated a fixed positive charge in the insulator of 1.5 "< 1012 cm -2 for p-type substrates and 4.0 × I0 t~ cm -2 for ntype substrates. Majority carrier trapping near the oxide/GaAs interface was reduced by annealing and a corresponding reduction of As at the interface was observed. The distribution of fast interface states on p-type substrates had a broad minimum of 7-10 :.: I0 *j cm -2 e V - t near midgap while the distribution of fast interface states displayed a peak of over 1013cm -2 eV -I near midgap on n-type samples. No corresponding difference in the Auger composition profiles were observed between n- and p-type samples. L S Chester and G Y Robinson, J Vac Sci Technol, 15 (4), 1978, 1525-1529.
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4213. Analysis of the oxide/semiconductor interface using Auger and ESCA as applied to InP and GaAs. (USA) This paper compares the Auger and ESCA techniques used to characterize the interfaces of thermally grown and anodic oxides of InP and GaAs. In the anodic oxide of GaAs, the Ga-O bonding extends deeper into the GaAs than the As-O bonding. In the anodic oxide of InP, both the P-O and In-O bonding penetrate to the same depth. The anodic oxide-GaAs interface changes with electrolyte. There is elemental P at the interface of the thermal oxide on InP, but it was not possible to prove or disprove the existence of elemental As at the anodic oxide/GaAs interface. It was found that the ESCA technique provided much needed bonding information which greatly facilitates characterizing the interface. It appears essential that both composition and bonding be determined. C W Wilmsen and R W Kee, J Vac Sci Technol, 15 (4), 1978, 15131517. 36 4214. Auger profiling studies of LPE n-AIxGal_~As-n-GaAs heterojunctions and the absence of rectification. (USA) Grading of the heterojunction interface has previously been proposed to explain the absence of rectification for LPE n-n heterojunctions. In this study, Auger profiles were made of LPE n-AlxGal_~,As-nGaAs (doped 10 ~s to 10 t 6 c m - 3 in both layers) which had been grown to minimize any barrier lowering due to the grading width and high carrier concentration. In a specific case, the calculated interface widths necessary to eliminate the barrier was greater than 500A; however, the measured interface width was less than 150A,. Ion profiling effects such as preferential sputtering, knock-on and substrate surface roughness would only increase the measured interface width. Although the measured interface width was much less than that required by theory to remove the barrier in the conduction band, the samples did not exhibit rectification. This indicates that the present grading model may be insufficient to explain the lack of rectification of these samples. C M Garner et al, J Vac Sci Technol, 15 (4), 1978, 1480-1482. 36 4215. XPS measurements of abrupt Ge-GaAs heterojnncfion interfaces. (USA) A method has been developed to grow thin epitaxial layers of Ge on GaAs substrates within an XPS system by an evaporative MBE technique. Abrupt heterojunctions with Ge layer thicknesses of ~ 2 0 , ~ have been grown on (111), (II0) and (100) GaAs crystal faces. By using XPS data obtained on these heterojunctions, variations in band gap discontinuities related to the crystallographic orientation dependence of interface dipoles have been observed directly. The data are also used to make an initial estimate of the valence band discontinuity for the abrupt Ge-GaAs heterojunction and with refinement of the technique, accurate values for this quantity should be obtainable. R W Grant et al, J Vac Sci Technol, 15 (4), 1978, 1451-1455.
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4213. Analysis of the oxide/semiconductor interface using Auger and ESCA as applied to InP and GaAs. (USA) This paper compares the Auger and ESCA techniques used to characterize the interfaces of thermally grown and anodic oxides of InP and GaAs. In the anodic oxide of GaAs, the Ga-O bonding extends deeper into the GaAs than the As-O bonding. In the anodic oxide of InP, both the P-O and In-O bonding penetrate to the same depth. The anodic oxide-GaAs interface changes with electrolyte. There is elemental P at the interface of the thermal oxide on InP, but it was not possible to prove or disprove the existence of elemental As at the anodic oxide/GaAs interface. It was found that the ESCA technique provided much needed bonding information which greatly facilitates characterizing the interface. It appears essential that both composition and bonding be determined. C W Wilmsen and R W Kee, J Vac Sci Technol, 15 (4), 1978, 15131517. 36 4214. Auger profiling studies of LPE n-AIxGal_~As-n-GaAs heterojunctions and the absence of rectification. (USA) Grading of the heterojunction interface has previously been proposed to explain the absence of rectification for LPE n-n heterojunctions. In this study, Auger profiles were made of LPE n-AlxGal_~,As-nGaAs (doped 10 ~s to 10 t 6 c m - 3 in both layers) which had been grown to minimize any barrier lowering due to the grading width and high carrier concentration. In a specific case, the calculated interface widths necessary to eliminate the barrier was greater than 500A; however, the measured interface width was less than 150A,. Ion profiling effects such as preferential sputtering, knock-on and substrate surface roughness would only increase the measured interface width. Although the measured interface width was much less than that required by theory to remove the barrier in the conduction band, the samples did not exhibit rectification. This indicates that the present grading model may be insufficient to explain the lack of rectification of these samples. C M Garner et al, J Vac Sci Technol, 15 (4), 1978, 1480-1482. 36 4215. XPS measurements of abrupt Ge-GaAs heterojnncfion interfaces. (USA) A method has been developed to grow thin epitaxial layers of Ge on GaAs substrates within an XPS system by an evaporative MBE technique. Abrupt heterojunctions with Ge layer thicknesses of ~ 2 0 , ~ have been grown on (111), (II0) and (100) GaAs crystal faces. By using XPS data obtained on these heterojunctions, variations in band gap discontinuities related to the crystallographic orientation dependence of interface dipoles have been observed directly. The data are also used to make an initial estimate of the valence band discontinuity for the abrupt Ge-GaAs heterojunction and with refinement of the technique, accurate values for this quantity should be obtainable. R W Grant et al, J Vac Sci Technol, 15 (4), 1978, 1451-1455.