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We report the effect of different temperature profiles on the quality of the InGaN/GaN multiple quantum well (MQW) structures by employing photoluminescence (PL) and atomic force microscopy (AFM). We adopted a two-step varied-barrier-growth temperature method to improve the structural and optical properties of the InGaN/GaN MQW layers. The low-temperature GaN barrier layer was introduced to reduce the desorption rate of the indium atoms of the InGaN well, and then the high-temperature GaN barrier was grown to reduce the defects of InGaN/GaN MQWs. When the width of the low-temperature GaN barrier was 50 Å and the high-temperature GaN barrier was grown at 1000 • C, the defect and surface roughness were significantly reduced, especially with a reduction in the depth of V-defect as low as 20 Å.

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In0.2Ga0.8N/In0.03Ga0.97N 3-period multiple quantum wells (MQWs) were grown by low pressure metalorganic chemical vapor deposition and the effects of pre-In flow prior to QW growth on its overall optical property were investigated. Pre-In flow did not change the structural property of the MQW structure such as In composition and period but strongly influenced its optical properties. MQW samples grown with pre-In flow exhibited longer peak wavelength and stronger peak intensity. CL measurement revealed more uniform and smaller emission centers in pre-In flow samples, implying a reduction of non-radiative defective regions and more In-rich regions. These results indicate that the In source introduced prior to QW growth preferentially gets incorporated around defect sites such as threading dislocations to inhibit their propagation while forming seeds for In-rich regions.