Temperature Dependence of Electron and Hole Impact Ionization Coefficients in GaN

Lina Cao,Patrick J. Fay,Jingshan Wang,Hansheng Ye,Galen Harden,Zhongtao Zhu,Anthony Hoffman

doi:10.1109/ted.2021.3054355

Abstract

The temperature dependence of the electron and hole impact ionization coefficients in GaN has been investigated experimentally. Two types of p-i-n diodes grown on bulk GaN substrates have been fabricated and characterized, and the impact ionization coefficients for both electrons and holes have been extracted using the photomultiplication method. Both the electron and hole impact ionization coefficients decrease as the temperature increases. The Okuto–Crowell model was used to describe the temperature dependence of the electron and hole impact ionization coefficients. Based on the measured impact ionization coefficients, the temperature dependence of the breakdown voltage of GaN non-punch through p-n diodes can be predicted; good agreement with experimentally reported results is obtained.

Highlights

G ALLIUM nitride is very attractive for high power RF and mm-wave amplification and is emerging for lower frequency power conversion and control applications, due to its high mobility, high saturation velocity, and high critical electric field
Maeda has only reported the temperature dependence of GaN’s effective impact ionization coefficients with the assumption of αeff ≡ α = β, while we have reported the temperature dependence of GaN’s electron and hole impact ionization coefficients separately
The breakdown and avalanche multiplication characteristics of GaN p-i-n diodes grown on native GaN substrates have been investigated

Summary

INTRODUCTION

G ALLIUM nitride is very attractive for high power RF and mm-wave amplification and is emerging for lower frequency power conversion and control applications, due to its high mobility, high saturation velocity, and high critical electric field. Cao et al [7], [8] have measured the electron and hole impact ionization coefficients using both wavelength-selective photomultiplication and noise spectral density measurements based on p-n junctions with a thin pseudomorphic In0.07Ga0.93N layer grown on bulk GaN substrates, but no temperature dependence was reported. Maeda et al [10], [11] extracted the impact ionization coefficients utilizing the Franz–Keldysh effect based on the p−/n+ diodes grown on bulk GaN substrates This approach requires additional assumptions, about the optical absorption profile in the material. The impact ionization coefficients of electrons and holes in GaN were experimentally determined from 298 to 398 K using the photomultiplication method based on two p-i-n structures grown on bulk GaN substrates. The temperature dependence of the breakdown voltage of GaN nonpunchthrough p-n diodes has been predicted and compared to experimental results

DEVICE DESIGN AND FABRICATION

RESULTS AND DISCUSSION

CONCLUSION