Influences of stress on the properties of GaN/InGaN multiple quantum well LEDs grown on Si （111） substrates

The influences of stress on the properties of InGaN/GaN multiple quantum wells （MQWs） grown on silicon substrate were investigated. The different stresses were induced by growing InGaN and A1GaN insertion layers （IL） respectively before the growth of MQWs in metal-organic chemical vapor deposition （MOCVD） system. High resolution x-ray diffrac- tion （HRXRD） and photoluminescence （PL） measurements demonstrated that the InGaN IL introduced an additional ten- sile stress in n-GaN, which released the strain in MQWs. It is helpful to increase the indium incorporation in MQWs. In comparison with MQWs without the IL, the wavelength shows a red-shift. A1GaN IL introduced a compressive stress to compensate the tensile stress, which reduces the indium composition in MQWs. PL measurement shows a blue-shift of wavelength. The two kinds of ILs were adopted to InGaN/GaN MQWs LED structures. The same wavelength shifts were also observed in the electroluminescence （EL） measurements of the LEDs. Improved indium homogeneity with InGaN IL, and phase separation with A1GaN IL were observed in the light images of the LEDs.