Numerical modeling of abrupt heterojunctions using a thermionic-field emission boundary condition

We present a numerical model in which the thermionic and tunneling mechanisms across an abrupt heterojunction interface are taken into account on the basis of the one dimensional drift-diffusion formulation. We use an expression of thermionic-field emission current formulated based on the WKB approximation as a boundary condition at the abrupt heterointerface which eventually limits the current transport over the barrier while maintaining the current continuity. The I-V characteristics of three types of GaAs/AlGaAs heterojunctions are analyzed by varying device dimension, doping density, and temperature and compared with those obtained by the thermionic emission model to illustrate the significance of both tunneling and thermionic emission mechanisms. We demonstrate that the role of tunneling in the overall current transport is very important in these abrupt heterojunctions especially at high doping densities and low temperatures. In the case of an MBE-grown AlGaAs triangular heterojunction barrier, the temperature-dependent I-V characteristics are measured and compared with the theoretical results. Good agreement is obtained when the tunneling process is taken into account by employing the thermionic-field emission boundary condition presented here.

[1]  M. Lundstrom,et al.  Numerical analysis of heterostructure semiconductor devices , 1983, IEEE Transactions on Electron Devices.

[2]  L. Eastman,et al.  A study of the conduction properties of a rectifying nGaAs-n(Ga, Al)As heterojunction , 1980 .

[3]  W. Fawcett,et al.  Monte Carlo determination of electron transport properties in gallium arsenide , 1970 .

[4]  K. Morizuka,et al.  Emitter—Base bandgap grading effects on GaAlAs/GaAs heterojunction bipolar transistor characteristics , 1985, IEEE Transactions on Electron Devices.

[5]  S. S. Perlman,et al.  p-n heterojunctions , 1964 .

[6]  D. E. Aspnes,et al.  GaAs lower conduction-band minima: Ordering and properties , 1976 .

[7]  P. Dapkus,et al.  Optimizing N-p-n and P-n-p heterojunction bipolar transistors for speed , 1987, IEEE Transactions on Electron Devices.

[8]  J. Lambe,et al.  Tunneling in Solids , 1973 .

[9]  C. R. Crowell,et al.  Normalized thermionic-field (T-F) emission in metal-semiconductor (Schottky) barriers , 1969 .

[10]  T. Sudo,et al.  A numerical analysis of a heterostructure InP/InGaAs photodiode , 1983, IEEE Transactions on Electron Devices.

[11]  R. Fischer,et al.  Comprehensive analysis of Si-doped Al x Ga 1-x As (x=0 to 1): Theory and experiments , 1984 .

[12]  M. Lundstrom.  Boundary conditions for pn heterojunctions , 1984 .

[13]  S. Bandyopadhyay,et al.  A rigorous technique to couple Monte Carlo and drift-diffusion models for computationally efficient device simulation , 1987, IEEE Transactions on Electron Devices.

[14]  M. Lundstrom,et al.  Thermionic emission-diffusion theory of isotype heterojunctions , 1984 .

[15]  W. Wiegmann,et al.  New rectifying semiconductor structure by molecular beam epitaxy , 1980 .

[16]  Chun-Yen Chang,et al.  Carrier transport across metal-semiconductor barriers , 1970 .

[17]  Kazushige Horio,et al.  Numerical modeling of heterojunctions including the thermionic emission mechanism at the heterojunction interface , 1990 .

[18]  G. Haddad,et al.  Ensemble Monte Carlo characterization of graded AlxGa1−xAs heterojunction barriers , 1990 .

[19]  H. Morkoc,et al.  An investigation of the effect of graded layers and tunneling on the performance of AlGaAs/GaAs heterojunction bipolar transistors , 1984, IEEE Transactions on Electron Devices.

[20]  Improved relaxation-time formulation of collision terms for two-band hydrodynamic models , 1989 .

[21]  J.R. Hauser,et al.  A computer analysis of heterojunction and graded composition solar cells , 1977, IEEE Transactions on Electron Devices.

[22]  Tsuyoshi Uda,et al.  A two-dimensional device simulator of semiconductor lasers , 1987 .