Study of low-frequency noise in GaN-on-Si films obtained by laser-assisted debonding

We report the growth of high-mobility Si-doped GaN epilayers utilizing unique double buffer layer (DBL) structures, which consist of a thin buffer layer (TBL) and a thick GaN intermediate-temperature buffer layer (ITBL). In this study, three types of DBL were investigated: (i) thin low-temperature GaN buffer layer (LTBL)/GaN ITBL (type I); (ii) nitridated Ga metal film/GaN ITBL (type II); and (iii) AlN high-temperature buffer layer (HTBL)/GaN ITBL (type III). It is found that the electron mobilities of the GaN films are substantially improved with the use of DBLs. The sample grown using type II DBL has the highest room temperature electron mobility of 450 cm2V-1s-1, yet the sample grown with type III DBL exhibit the highest overall electron mobility of 520 cm2V-1s-1 at around 200K. The PL results show that the sample deposited on type III DBL exhibit the highest compressive stress at room temperature. The data suggest that the use of type III DBL leads to the relaxation tensile stress at the growth temperature resulting in the improvements in the crystallinity and defect properties. Due to the mismatch in the coefficients of expansion between GaN and sapphire the sample with the highest compressive stress at room temperature corresponds to the one with the lowest tensile stress at the growth temperature. It was shown that low tensile stress facilitates two-dimensional growth leading to improvements in the crystallinity and defect properties. This is supported by the experimental results of low-frequency noise measurements, which indicated substantial reduction in the flicker noise level as well as the elimination of deep-levels with the use of type III DBL.