Polarization imaging of imperfect m-plane GaN surfaces

Yuji Sakai,Masayoshi Tonouchi,Hidetoshi Nakanishi,Iwao Kawayama

doi:10.1063/1.4979511

Abstract

Highlights

Future ultraviolet optical devices and high-power/high-voltage devices rely on the wide band gap semiconductor GaN.[1,2] The characteristics of devices with c-plane GaN are highly affected by strong spontaneous and piezoelectric polarizations along the c-axis
The strong built-in electric fields generated by these polarizations cause an undesirable redshift in the radiation frequency through the quantum confined Stark effect[3] and the degradation of luminous efficiency due to the spatial separation of electrons and holes[4] in heterostructure light-emitting diodes (LEDs) based on c-plane GaN
Power devices with c-plane GaN-based transistors work mostly as normally on devices in which current flows without a gate bias because of the surface electric field induced by the piezoelectric and spontaneous polarization, while a normally off transistor is strictly required for the safe operation of GaN power devices

Summary

Introduction

Future ultraviolet optical devices and high-power/high-voltage devices rely on the wide band gap semiconductor GaN.[1,2] The characteristics of devices with c-plane GaN are highly affected by strong spontaneous and piezoelectric polarizations along the c-axis. We report on the surface polar state distribution of m-plane GaN wafers using a laser terahertz emission microscope (LTEM).

Results

Conclusion