Strain modulation effect of superlattice interlayer on InGaN/GaN multiple quantum well

Abstract

The strong piezoelectric field 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 influence and mechanism of strain modulation in the InGaN/GaN superlattice (SL), epitaxial wafers with an n-type InGaN/GaN SL interlayer sample, and their corresponding control samples are prepared. The measured temperature-dependent photoluminescence (PL) spectra of the epitaxial wafers, show that the introduction of an SL interlayer leads to a shorter-wavelength emission and enhancement of 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 increasing 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 indicate that the incorporation of a superlattice interlayer can partly suppress the quantum-confined Stark effect (QCSE) that affects the light emission efficiency. Theoretical calculations show that the introduction of a superlattice strain layer before growing an active multiple quantum well can weaken the polarization-induced built-in electric field in the active quantum well, reduce the tilt of the energy band 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 recombination and non-radiative recombination, thereby achieving higher recombination efficiency and improving 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.