- Email: [email protected]
Current transport in metal-semiconductor barriers
A B S T R A C T S ON M I C R O E L E C T R O N I C S AND R E L I A B I L I T Y
249
circuits. The open and sealed tube techniques are treated. Materials used in solid, liquid and gas diffusions, and their advantages and disadvantages are dealt with. ]. F. LIBSCH,S C P and Solid State Technology, October (1966), p. 37. The contributions of induction beating to solid state technology are presented. The areas of application include the production of ultra-pure materials by zone refining and zone levelling, the growth of both metallic and non-metallic single crystals, thin-film production and epitaxial growth. Sealing operations, soldering of printed circuit terminals and the assembly of diodes, solar cells and micro-modules are also discussed.
Induction heating and solid state technology.
Metal-semiconductor surface barriers. C. A. MEAD,Solid St. Electron. 9 (1966), p. 1023. The physical principles underlying the metal-semiconductor barrier are discussed in the light of recent experimental results. A semi-empirical approach for predicting the type of contact to be expected at an arbitrary metal-semiconductor interface is presented.
Current transport in metal-semiconductor barriers. C. R. CROWELL and S. M. SzE, Solid St. Electron. 9 (1966), p. 1035. A theory for calculating the magnitude of majority carrier current flow in metal-semiconductor barriers is developed which incorporates Schottky's diffusion (D) theory and Bethe's thermionic emission (T) theory into a single T - D emission theory, and which includes the effects of the image force. A low electric field limit for application of this theory is estimated from consideration of phonon-induced backscattering near the potential energy maximum. A high electric field limit associated with the transition to T - F emission is estimated from calculations of the quantummechanical transmission of a Maxwellian distribution of electrons incident on the barrier. The theory predicts a wide range of electric field ~ 2 × 105 to 4 × 10s V/cm over which the T - D theory may be applied to metal-n-type Si barriers at 300°K. The corresponding range for metal-n-type GaAs barriers is 9 × 103 to 8 × 104 V/cm at 300°K. The decreased upper limit is due mainly to the smaller electron effective mass in GaAs, the increased lower limit to a small optical-phonon energy and a shorter electron-optical-phonon mean-free path. The theory predicts Richardson constants of 96 and 4.4 A/cm2/°K ~ for metal-n-type Si and metal-n-type GaAs barriers respectively. Experimental measurements on both metal-Si and metal-GaAs barriers are in general agreement with the theory. Values of the barrier n[=(q/kT)(dV/d ln y)] appreciably greater than unity are predicted for the field-dependent barrier height which occurs when an interface layer of the order of atomic thickness exists between the metal and the semiconductor. A field dependence of the barrier height is shown to have no first order effect on the derivative of the 1/C 2 vs. V relationship for the barrier. The intercept of a 1/C 2 vs. V plot is shown to yield the barrier height extrapolated linearly to zero field in the semiconductor. Experimental evidence for the existence of interface layers in near-ideal Schottky barriers is also presented.
nGe-pGaAs heterojunctions. A. R. RIBEN and D. L. FEUCHT,Solid St. Electron. 9 (1966), p. 1055. Experiments on nGe-GaAs heterojunctions are presented which show that the previous diffusion or emission theories of current transport do not satisfactorily explain the observed electrical characteristics. These measurements indicate, however, that the basic Anderson model for abrupt heterojunctions is valid. Tunnelling is considered as an alternate transport mechanism. A recombination tunnelling model in the forward direction and a Zener tunnelling model in the reverse direction are proposed to describe the functional behaviour of the current as a function of voltage and temperature.
The role of adsorption in heterogeneous vapor-solid nucleation. R. D. GRETZ, J. Phys. Chem. Solids, 27 (1966), p. 1849. The role of adsorption on a substrate in heterogeneous nucleation of crystals from vapor is considered in detail. It is found that there are two major classifications of adsorption kinetics: (1) steady-state concentration and (2) time-dependent concentration, which significantly alter the definition of supersaturation in an adsorbed layer on the substrate. The resultant characterization provides two general descriptions common to all three available theories of heterogeneous vapor-solid nucleation. The key assumption of adsorbed molecule-critical nucleus equilibrium made in these theories is experimentally found to be the case for nucleation of silver on tungsten, a system where vaporsubstrate equilibrium is not achieved. In this case a temperature independent critical concentration for nucleation is found and it is suggested that this may be the most important aspect of heterogeneous
249
circuits. The open and sealed tube techniques are treated. Materials used in solid, liquid and gas diffusions, and their advantages and disadvantages are dealt with. ]. F. LIBSCH,S C P and Solid State Technology, October (1966), p. 37. The contributions of induction beating to solid state technology are presented. The areas of application include the production of ultra-pure materials by zone refining and zone levelling, the growth of both metallic and non-metallic single crystals, thin-film production and epitaxial growth. Sealing operations, soldering of printed circuit terminals and the assembly of diodes, solar cells and micro-modules are also discussed.
Induction heating and solid state technology.
Metal-semiconductor surface barriers. C. A. MEAD,Solid St. Electron. 9 (1966), p. 1023. The physical principles underlying the metal-semiconductor barrier are discussed in the light of recent experimental results. A semi-empirical approach for predicting the type of contact to be expected at an arbitrary metal-semiconductor interface is presented.
Current transport in metal-semiconductor barriers. C. R. CROWELL and S. M. SzE, Solid St. Electron. 9 (1966), p. 1035. A theory for calculating the magnitude of majority carrier current flow in metal-semiconductor barriers is developed which incorporates Schottky's diffusion (D) theory and Bethe's thermionic emission (T) theory into a single T - D emission theory, and which includes the effects of the image force. A low electric field limit for application of this theory is estimated from consideration of phonon-induced backscattering near the potential energy maximum. A high electric field limit associated with the transition to T - F emission is estimated from calculations of the quantummechanical transmission of a Maxwellian distribution of electrons incident on the barrier. The theory predicts a wide range of electric field ~ 2 × 105 to 4 × 10s V/cm over which the T - D theory may be applied to metal-n-type Si barriers at 300°K. The corresponding range for metal-n-type GaAs barriers is 9 × 103 to 8 × 104 V/cm at 300°K. The decreased upper limit is due mainly to the smaller electron effective mass in GaAs, the increased lower limit to a small optical-phonon energy and a shorter electron-optical-phonon mean-free path. The theory predicts Richardson constants of 96 and 4.4 A/cm2/°K ~ for metal-n-type Si and metal-n-type GaAs barriers respectively. Experimental measurements on both metal-Si and metal-GaAs barriers are in general agreement with the theory. Values of the barrier n[=(q/kT)(dV/d ln y)] appreciably greater than unity are predicted for the field-dependent barrier height which occurs when an interface layer of the order of atomic thickness exists between the metal and the semiconductor. A field dependence of the barrier height is shown to have no first order effect on the derivative of the 1/C 2 vs. V relationship for the barrier. The intercept of a 1/C 2 vs. V plot is shown to yield the barrier height extrapolated linearly to zero field in the semiconductor. Experimental evidence for the existence of interface layers in near-ideal Schottky barriers is also presented.
nGe-pGaAs heterojunctions. A. R. RIBEN and D. L. FEUCHT,Solid St. Electron. 9 (1966), p. 1055. Experiments on nGe-GaAs heterojunctions are presented which show that the previous diffusion or emission theories of current transport do not satisfactorily explain the observed electrical characteristics. These measurements indicate, however, that the basic Anderson model for abrupt heterojunctions is valid. Tunnelling is considered as an alternate transport mechanism. A recombination tunnelling model in the forward direction and a Zener tunnelling model in the reverse direction are proposed to describe the functional behaviour of the current as a function of voltage and temperature.
The role of adsorption in heterogeneous vapor-solid nucleation. R. D. GRETZ, J. Phys. Chem. Solids, 27 (1966), p. 1849. The role of adsorption on a substrate in heterogeneous nucleation of crystals from vapor is considered in detail. It is found that there are two major classifications of adsorption kinetics: (1) steady-state concentration and (2) time-dependent concentration, which significantly alter the definition of supersaturation in an adsorbed layer on the substrate. The resultant characterization provides two general descriptions common to all three available theories of heterogeneous vapor-solid nucleation. The key assumption of adsorbed molecule-critical nucleus equilibrium made in these theories is experimentally found to be the case for nucleation of silver on tungsten, a system where vaporsubstrate equilibrium is not achieved. In this case a temperature independent critical concentration for nucleation is found and it is suggested that this may be the most important aspect of heterogeneous