Optical characterization of InGaN/GaN multiple quantum well structures grown by metalorganic chemical vapor deposition

Abstract

Optical and crystal properties of InGaN/GaN multiple quantum well (MQW) structures grown by metalorganic chemical vapor deposition (MOCVD) were characterized using room-temperature photoluminescence (PL) and high-resolution Xray diffraction (HRXRD), respectively. The near bandgap excitonic peak decreased from 2.77 eV to 2.68 eV while there was a 10 Å increase in the well thickness, probably caused by variations of quantized energy levels. In addition, higher growth temperature of MQW structures had a small influence on the pair thickness, but the emission wavelength showed a blueshift attributed to the decrease in average of indium mole fraction. However, the near bandgap excitonic peak remained constant for the thicker quantum barriers. For the PL emission intensity of InGaN/GaN MQW structures, it was enhanced with a thinner quantum well width and a thicker quantum barrier, which could be resulted from the improvement of optical confinement in the quantum well. Moreover, by using the higher growth temperature, enhanced PL intensity was achieved due to the improvement of structure quality for the InGaN/GaN heterostructure. Therefore, these results suggest that the emission wavelength and intensity of the InGaN/GaN MQW-based optical device could be modulated by designing thicknesses of quantum wells as well as growth temperatures of MQW structures.