Terahertz radiation generated by acoustic waves in InGaN/GaN Multiple Quantum Wells

InGaN/GaN multiple quantum wells (MQWs) are widely studied for light emitting diodes (LEDs) and laser diodes (LDs). However, the lattice mismatch and miscibility between GaN and InN, the diffusion and segregation of indium in MQW due to high-temperature growth, change the potential distribution in MQW, results in degradation of the optical properties of devices. Therefore, if a nondestructive evaluation method of the potential change in the MQW structure can be realized, it can greatly contribute to the improvement of LDs and LEDs with MQWs. We have been conducting research using laser-induced terahertz (THz) emission as an evaluation method for semiconductor surfaces and interfaces [1, 2]. In this study, we observed THz emissions from InGaN/GaN MQWs excited by a femtosecond (fs) laser and investigated generation mechanism of THz waves based on detailed characterization of the THz emissions with the aim of developing it as an evaluation method of MQW in the future.