Photoluminescence mapping and time-domain thermo-photoluminescence for rapid imaging and measurement of thermal conductivity of boron arsenide

Abstract

Cubic boron arsenide (BAs) is attracting greater attention due to the recent experimental demonstration of ultrahigh thermal conductivity above 1000 W/m·K. However, its bandgap has not been settled and a simple yet effective method to probe its crystal quality is missing. Furthermore, traditional  measurement methods are destructive and time consuming, thus they cannot meet the urgent demand for fast screening of high  materials. After we experimentally established 1.82 eV as the indirect bandgap of BAs and observed room-temperature band-edge photoluminescence, we developed two new optical techniques that can provide rapid and non-destructive characterization of  with little sample preparation: photoluminescence mapping (PL-mapping) and time-domain thermo-photoluminescence (TDTP). PL-mapping provides nearly real-time image of crystal quality and  over mm-sized crystal surfaces; while TDTP allows us to pick up any spot on the sample surface and measure its  using nanosecond laser pulses.These new techniques reveal that the apparent single crystals are not only non-uniform in , but also are made of domains of very distinct . Because PL-mapping and TDTP are based on the band-edge PL and its dependence on temperature, they can be applied to other semiconductors, thus paving the way for rapid identification and development of high- semiconducting materials.

High ambipolar mobility in cubic boron arsenide revealed by transient reflectivity microscopy

“…S12 and S13). Clearly, the enhanced PL intensity observed in the c-BAs samples in the current study indicates that p-type doping has only introduced shallow acceptors rather than nonradiative deep levels (10,25). Because hot carriers can also be generated by electrical injection and low-intensity light, both hot carriers and fully relaxed carriers can be used for high-speed optoelectronic devices and highefficiency solar cells in conjunction with the high mobility of the band-edge carriers.…”

“…3B) (2,8). This gradually increased doping level toward the (111) surface is further supported by the corresponding increased PL intensity (10,25). P-type doping will result in reduced carrier mobility owing to the presence of ionized dopants (these dopants are already activated) and a lower electron mobility than hole mobility, because minority carriers will dominate the carrier dynamics.…”

“…PL mapping shown in the inset of Fig. 1D also indicates the uniform crystal quality on the (111) surface (10). We performed all measurements at room temperature and further characterized sample 1 and a second sample, labeled sample 2 (12) (fig.…”

Invariant expansion of the 30-band k.p model and its parameters for III-V compounds

“…The electronic band structures for BX compounds were calculated by DFT methods and reported in many articles [74][75][76][77][78], but experimental studies of the band gap for cubic BX are limited to a few cases [79][80][81][82][83][84][85], mostly for BAs. The interest in BAs increased suddenly in 2013 when DFT calculations predicted BAs as a highly thermal conductive material with a thermal conductivity comparable with that of diamond [86,87].…”

High ambipolar mobility in cubic boron arsenide

“…We used photoluminescence (PL) and Raman spectroscopies to identify the nonuniform impurity distribution in c-BAs ( 17 , 20 ). We measured the PL spectrum (Fig.…”