Correlation between deep-level defects and turn-on recovery characteristics in AlGaN/GaN hetero-structures

Abstract

We report on a correlation between deep-level defects and turn-on recovery characteristics in AlGaN/GaN hetero-structures, employing Schottky barrier diodes. Photo-capacitance spectroscopy measurements reveal three specific deep levels located at ∼2.07, ∼2.80, and ∼3.23 eV below the conduction band, presumably attributable to Ga vacancies and/or impurity C present in the GaN buffer layer. Additionally, from photo-assisted turn-on current recovery measurements, by using 390 and 370 nm long-pass filters, the recovery time becomes significantly faster due to inactivation of their corresponding deep-level traps. Therefore, the ∼2.80 and ∼3.23 eV levels are probably responsible for the carrier-trapping phenomena in the bulk region.

In situmeasurement of GaN film photoluminescence under plasma etching

“…On the one hand, the plasma introduces non-radiative defects on the top surface region of the GaN film [10,15,16], which may be the cause of the decrease of the NBE intensity, shown in Figure 5 and on the other hand, the YL observed is strongly related to deep-level defects, such as Ga vacancies and/or residual C impurities [17][18][19]. So, we consider that these deep-level defects vary after plasma etching, which leads to the decrease of the YL intensity.…”

Deep-level defects and turn-on capacitance recovery characteristics in AlGaN/GaN heterostructures

“…Additionally, for the simple short-time evaluation of the 2DEG carrier trapping in the GaN buffer layer, the turn-on capacitance recovery characteristics at a V G of 0 V after the off-state at various values of V G between −5 and −30 V were measured under various optical illuminations using the same Xe lamp coupled with three kinds of long-pass filters of 540, 390 and 370 nm. Here, the stressing time under the off-state was varied between 1 and 30 s. These photo-assisted turn-on capacitance recovery measurements have the same methodology as the turn-on current recovery measurements that we have previously reported, based on the deep-level defect energies [8]. specific deep-level defects [8][9][10].…”

“…Again, more details can be found in Refs. [8,11]. The fabricated SBDs were illuminated from the back side with monochromatic light obtained from a 150-W Xe lamp coupled with a high-resolution monochromator.…”

“…Additionally, these deep-level defects are probably associated with the bulkrelated current-collapse phenomenon, because the current collapses tend to become severe with increasing the concentrations of these deep levels in our previous study [10]. More importantly, we have recently reported that the C-related~2.80 and~3.23 eV levels are probably responsible for the 2DEG carrier trapping, using a simple correlation study between these specific deep-level defects and the turn-on current recovery characteristics [8]. In this study, we confirmed the viability of turn-on capacitance recovery measurements as a simple short-time method of evaluating 2DEG carrier trapping in the GaN buffer layer, employing Schottky barrier diodes (SBDs).…”

“…Additionally, novel device structures with gate field plates have also been reported to be effective in decreasing the current collapses by modifying the electric field at the gate edges [3]. Nevertheless, the current collapses have not yet been completely eliminated, and there is a strong need to investigate deep-level defects in the bulk region of AlGaN/GaN heterostructures from the viewpoint of 2DEG carrier trapping [4][5][6][7][8].…”