Exploration of Physicochemical Mechanism for Negative Bias Temperature Instability in GaN‐HEMTs by Extracting Activation Energy of Dislocations

Abstract

epitaxial layers on silicon enables the use of existing silicon manufacturing infrastructure, eliminating the need for costly specific production facilities and leveraging large diameter silicon wafers at low cost. [10,11] Although silicon is a relatively cheap substrate compared with other substrate candidates, but has some distinct disadvantages since silicon and GaN are unmatched material systems. [12] The discrepancies in crystalline structure of GaN and silicon leads to higher lattice mismatches, behaving like dislocations and other types of defects. [13][14][15][16] The crystal defects affect the device performance and reliability to a large extent. A typical conundrum in GaN filed is related to the fact that the dislocations/lattice mismatch could exert inevitable negative effects on the device's basic performance, stability, and reliability. [17][18][19][20] Intensive researches indicated that charge trapping process caused by defects significantly affect the device performance. [21][22][23][24][25][26][27] As the most promising power device, gallium nitride (GaN)-based high electron mobility transistors (HEMTs) typically works under high voltage over a prolonged period. The long-term accumulation of heat during the operation appears to be another unfavorable factor that deteriorates the reliability. [28][29][30][31] The general degradation of electrical performance under negative bias condition at elevated temperatures is collectively known as negative bias temperature instability (NBTI) problem. [32] Although the NBTI problem was first noticed and mainly discussed in p-MOSFET devices, [33][34][35][36] it also perplexes depletion-mode or normally-ON GaN-HEMTs which is the most frequently used GaN device. [37][38][39][40][41][42][43][44] NBTI-related issues in depletion-mode GaN-HEMTs with different kinds of dielectric layer have been investigated in a series of researches. [41,[45][46][47][48][49][50] The NBTI-induced reliability issues in GaN-HEMTs have been acknowledged as a major concern that contributes to the operational instability. While intensive efforts have been made to optimize it from the perspective of manufacturing process or selected materials, [45,51,52] insufficient attention has been devoted to fundamental understanding of the intrinsic mechanisms. Some studies [41][42][43][44][45][46] attributed the degradation to the charge and discharge process of defects at the interface of GaN buffer layer and dielectric layer, while others [47][48][49][50] considered the degradation cause is not only the interface