Defect analysis in GaN films of HEMT structure by cross-sectional cathodoluminescence

Abstract

Defect analysis of GaN films in high electron mobility transistor (HEMT) structures by cross-sectional cathodoluminescence (X-CL) is demonstrated as a useful technique for improving the current collapse of GaN-HEMT devices, and the relationship between crystal quality and device characteristics is also investigated. The crystal quality of intrinsic-GaN (i-GaN) and carbon-doped GaN produced clearly different peak intensities of blue luminescence (BL), yellow luminescence (YL), and band-edge emission (BE), which is independently detected by X-CL. Current collapse in GaN-HEMT devices is found to be determined by the BL/BE and YL/BE ratios at the top of the i-GaN layer, which is close to the channel. Moreover, the i-GaN thickness required in order to minimize the BL/BE and YL/BE ratios and the thickness dependency of GaN for minimizing the BL/BE and YL/BE ratios depending on the growth conditions can be evaluated by X-CL. However, there is no correlation between current collapse in GaN-HEMT devices and the YL/BE ratio by conventional photoluminescence because HEMT devices consist of multiple GaN layers and the YL signal is detected from the carbon-doped GaN layer. Thus, the X-CL analysis method is a useful technique for device design in order to suppress current collapse.

Three-dimensional band diagram in lateral polarity junction III-nitride heterostructures

“…2(a), the spectrum of the LPJ MQWs identifies two main peaks: one is located at ∼343 nm consistent with the PL (Fig. 1) attributed to the MQW emission; and the broad peak is related to deep levels such as donor-acceptor pair or transition from conduction band to deep acceptors [11]. The shorter wavelength of the CL MQW peak compared to that of the PL peak may be attributed to the band filling effect due to much higher excitation electron energy amid CL experiments.…”

Current Status of Carbon‐Related Defect Luminescence in GaN

“…[22] In this review, the until then identified PL bands in GaN are described and a detailed summary of their behavior, e.g., dependence on temperature, excitation power density, and doping, is given. Emanating from the importance of C doping for optoelectronic devices and the fact that luminescence methods are more and more often applied for device analysis, [11,[23][24][25][26][27] in this article we focus on the recent progress with respect to understanding the role of C in bulk GaN. Accordingly, we will emphasize the defect-related radiative transitions in the visible spectral region of carbon-doped bulk GaN.…”