砷化镓功率异质结双极晶体管

Abstract 

We demonstrate the results of two-dimensional (2-D)hydrodynamic simulations of one-finger power heterojunctionbipolar transistors (HBTs) on GaAs. An overview of the physicalmodels used and comparisons with experimental data are given.We present models for the thermal conductivity and the specificheat applicable to all relevant diamond and zinc-blende structuresemiconductors. They are expressed as functions of the lattice tem-perature and, in the case of semiconductor alloys, of the materialcomposition.

I.INTRODUCTION

ETEROJUNCTION bipolar transistors (HBTs) attract9much industrial interest because of their capability tooperate at high current densities [1],[2]. AlGaAs/GaAs orInGaP/GaAs-based devices are promising candidates for powerapplications in modern mobile telecommunication systemsHeat generated at the heterojunctions cannot completelyleave the device, especially in the case of Il-V semiconductormaterials. Therefore, significant self-heating occurs in thedevice and leads to a change of the electrical device character-1stics.

Heat generated at the heterojunctions cannot completelyleave the device, especially in the case of Ill-V semiconductormaterials. Therefore, significant self-heating occurs in thedevice and leads to a change of the electrical device characteristics.

Accurate simulations save expensive technological efforts toobtain significant improvements ofthe device performance. Thetwo-dimensional (2-D) device simulator MINIMOS-NT [3] isextended to deal with different complex materials and structures, such as binary and ternary semiconductor Ill-V alloyswith arbitrary material composition profiles. Various importantphysical effects, such as bandgap narrowing, surface recombination, and self-heating, are taken into account.This paper describes the physical models and gives examplesof simulations verified by measurements.

II.THE PHYSICAL MODELS

In previous work, we emphasized on bandgap narrowing asone of the crucial heavy-doping effects to be considered forbipolar devices (4]. We have developed a new physically-basedanalytical bandgap narrowing model, applicable to compound semiconductors, which accounts for the semiconductor material, the dopant species, and the lattice temperature. As the minority carrier mobility is of considerable importance for bipolartransistors, a new universal low field mobility model has beenimplemented in MINIMOS-NT (5]. It is based on Monte-Carlosimulation results and distinguishes between majority and minority electron mobilities Energy transport equations are necessary to account for nonlocal effects, such as velocity overshoot [6], [7]. In recent worka new model for the electron energy relaxation time has beenpresented (8]. It is based on Monte-Carlo simulation results andis applicable to all relevant semiconductors with diamond andzinc-blende structure. The energy relaxation times are expressedas functions of the carrier and lattice temperatures and in thecase of semiconductor alloys of the material composition.Considering the nature of the simulated devices (includingabrupt InGaP/GaAs and AlGaAs/InGaP heterointerfaces) andthe high electron temperatures observed at maximum bias weuse sophisticated thermionic-field emission interface models[9] in conjunction with the hydrodynamic transport model.At the other (homogeneous or graded) interfaces continuousquasi-Fermi levels were assumed.