Time-resolved photoluminescence spectral analysis of phonon-assisted DAP and e-A recombination in N+B-dopedn-type 4H-SiC epilayers

Abstract

It is crucial to clarify the roles of phonon-assisted donor-acceptor pairs (DAPs) and free-toacceptor (e-A) emissions in n-type 4H-SiC doped with nitrogen (N) and boron (B), where N and B induce the shallow donor and the D center (deep B) acceptor levels, respectively, in order to understand the complicated carrier recombination mechanism, as well as developing fluorescent SiC with a high color rendering index by controlling the ratio of the two overlapped emissions. Here, time-resolved photoluminescence (TRPL) spectral analyses were performed, in which phonon-assisted DAPs and e-A components were individually recognized. The D center-related green luminescence (1.6-2.8 eV) shows a non-exponential decay followed by a very slow decay in TRPL measurements at room temperature (RT). It emerges that most of the DAP emission intensities decay much faster than e-A emissions and contribute to what is initially fast and non-exponential decay at low temperatures, while the slow decay at RT is mainly from e-A emissions. At a much higher temperature, such as 473 K, only the e-A emission remains and the decay transforms from non-exponential to exponential behavior. High-temperature thermal quenching of e-A emissions exhibits different behaviors for samples with differing B doping concentrations. An activation energy of 0.6 eV was estimated from the Arrhenius plot of e-A emission intensity from a B-doped sample, which matches the D center level. This indicates that the hole thermal emission rate is greatly enhanced at a high temperature, which accelerates the decay of e-A emission intensity at high temperatures.

Polytype switching identification in 4H-SiC single crystal grown by PVT

“…In CL experiment two different peaks are identified in two different regions of the test sample. Therefore, these regions are related to defect states of SiC crystal and identified as region-1 is 4H-SiC polytype and region-2 is 6H-SiC polytype, respectively [26][27][28]. It is also confirmed by XRD and Raman scattering tools and to be discussed later.…”

“…Ou et al also observed shallow donor to deep acceptor-pair transition in SiC crystal (nitrogen to boron) around ~ 580-590 nm in 6H-SiC [26]. Liu et al and further Yang et al also identified Donor acceptor-pair emission (nitrogen to boron) for 4H-SiC crystal around 500-525 nm [27,28]. In CL experiment two different peaks are identified in two different regions of the test sample.…”

“…The central darkest contrast strip is 15R-SiC, the left side of bright contrast is 6H-SiC and the right side bright one is possibly 4H-SiC polytype. The possible plane of these polytypes is (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28), (11-2 12) and (11-2 30) for 4H-SiC, 6H-SiC and 15R-SiC, respectively. Near the interface of 6H-SiC and 15R-SiC, some elliptical dark regions are also noticed and these regions may be micropipes or bunching of threading screw dislocations.…”

Effects of stacking faults on electron transport in 4H-SiC n-type epilayers under unipolar operation evaluated by TCAD simulation

“…[28][29][30][31][32][33][34][35][36] In fact, techniques to prevent the bipolar degradation were developed by locally controlling a minority carrier lifetime in an epilayer. [37][38][39] However, there exist few fundamental studies which quantitatively explain the mechanisms of the degradation in the electrical conduction due to the stacking faults (SFs), though the problem may be qualitatively discussed based on a quantum well model, i.e. the SF acts as a quantum well in the conduction band and trapped immobile electrons in the quantum well create a potential barrier for conduction electrons, resulting in the disturbance of electron transport.…”