Study on the strain modulation effect of superlattice interlayer on InGaN/GaN multiple quantum well

Abstract

The strong piezoelectric field present in InGaN/GaN heterostructure quantum wells severely reduces the light emission efficiency of multiple quantum well (MQW) structures. To address this issue, a strain modulation interlayer is commonly used to mitigate the piezoelectric polarization field and improve the luminescence performance of the devices. To investigate the impact and mechanism of strain modulation in the InGaN/GaN superlattice (SL), epitaxial wafers were fabricated with an n-type InGaN/GaN SL interlayer sample, along with a corresponding control sample. By measuring the temperature-dependent photoluminescence (PL) spectra of the epitaxial wafers, experimental results show that the introduction of an SL interlayer leads to a shorter emission wavelength and an enhanced internal quantum efficiency. As the temperature increases, a blue shift of the PL peak is observed. However, for the sample with an SL interlayer, the blue shift of the PL peak with temperature is relatively small. Electroluminescence (EL) experiments indicate that the introduction of an SL interlayer significantly increases the integrated intensity of the EL peak and reduces its full width at half maximum. These phenomena collectively suggest that the incorporation of a superlattice interlayer can partially suppress the quantum-confined Stark effect (QCSE) that affects the light emission efficiency. Theoretical calculations demonstrated that the introduction of a superlattice strain layer before the growth of the multiple quantum well active region can weaken the polarization-induced built-in electric field, reduce the tilt of the energy bands in the multiple quantum well active region, increase the overlap of electron and hole wave functions, enhance the emission probability, shorten the radiative recombination lifetime, and promote competition between radiative and non-radiative recombination, thereby achieving higher recombination efficiency and improved light emission intensity. This study provides experimental and theoretical evidence that the strain modulation SL interlayer can effectively improve the device performance and offer guidance for optimizing the structural design of devices.