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

Abstract

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.

Electrical characterization of vacuum-deposited p-CdTe/n-ZnSe heterojunctions

“…Whereas in heterojunctions, I-V characteristic depends also on thermionic emission across the interface in low doping level and the tunnel current in high-doped semiconductors. Several authors have proposed and verified models on conduction mechanism in heterojunctions (Chang 1965;Yang et al 1993;Bhapkar and Mattauch 1993;Horio and Yanai 1990;Cavallini and Polenta 2008), which are similar to thermionic emission and diffusion model proposed by Sze and Crowell for a metal-semiconductor junction (Crowell and Sze 1966). Hence, the I-V characteristics of p-CdTe/n-ZnSe heterojunction have general form…”

Toward reversing Joule heating with a phonon-absorbing heterobarrier

“…The local potential distribution can be controlled by an external potential, such as the gate voltage [13,14] which requires additional structure, but here we employ the band discontinuity of the heterojunction [15,16]. The bandgap discontinuity is controlled by alloying (here Al composition), and in particular the discontinuity in the conduction band (∆E e,c ) is the potential barrier with height ϕ b for the electrons.…”

Multiscale modeling of solar cells with interface phenomena

“…To do so, we use a model used in physical engineering literature [18,19], which does not have the same "DDM-like" formulation as that given for potential equation by (46) and (47)…”

“…Finally, we mention that in some works [18] the continuity equation on the interface extending (49) may account for additional interface phenomena, i.e., interface traps, via additional right-hand-side interface terms active only in Ω I , i.e., at I. We do not consider these here.…”

“…However, by (18) we have to deal with nonlinear dependence of D n on the variables involved. Thus, even though the first order approximation is less accurate, it appears also to be the most straightforward.…”