Modulation of polarization field by fluorine ions in AlGaN/GaN heterostructures revealed by positron annihilation spectroscopy

✍ Scribed by Wang, Maojun ;Cheng, Chung Choi ;Beling, Chris D. ;Fung, Stevenson ;Chen, Kevin J.

• Book ID: 105365805
• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 296 KB
• Volume: 207
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/pssa.200983463

✦ Synopsis

Abstract

Modulations of energy band and polarization field by fluorine ions in fluorine plasma treated AlGaN/GaN heterostructures were revealed by positron annihilation spectroscopy (PAS). It is found that the annihilation probability is mainly governed by the electric field in the AlGaN/GaN heterostructure, which could be modulated by charged ions, opposite to what was first expected from the large number of plasma‐induced defects such as Ga‐vacancies. The modulation of electric field is successfully observed through the opposite changes in the S parameters on the two sides of the hetero‐interface after fluorine plasma treatment due to the opposite E‐field directions. Fluorine is experimentally proved to be negatively charged in GaN related materials, which is consistent with the operation principle of enhancement‐mode AlGaN/GaN HEMT fabricated by fluorine plasma treatment. It is also suggested that PAS is a useful tool to probe the intrinsic electric field in AlGaN/GaN system.