Influence of surface states on deep level transient spectroscopy in AlGaN/GaN heterostructure**Project supported by the National Key Basic Research Program of China (Grant No. 2011CBA00606), the Program for New Century Excellent Talents in University, China (Grant No. NCET-12-0915), and the National Natural Science Foundation of China (Grant Nos. 61334002 and 61404097).

Abstract

Deep level transient spectroscopy (DLTS) as a method to investigate deep traps in AlGaN/GaN heterostructure or high electron mobility transistors (HEMTs) has been widely utilized. The DLTS measurements under different bias conditions are carried out in this paper. Two hole-like traps with active energies of Ev + 0.47 eV, and Ev + 0.10 eV are observed, which are related to surface states. The electron traps with active energies of Ec − 0.56 eV are located in the channel, those with Ec − 0.33 eV and Ec − 0.88 eV are located in the AlGaN layer. The presence of surface states has a strong influence on the detection of electron traps, especially when the electron traps are low in density. The DLTS signal peak height of the electron trap is reduced and even disappears due to the presence of plentiful surface state.