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Home > News > Effects of lift-off and strain relaxation on optical properties of InGaN/GaN blue LED grown on 150 mm diameter Si (111) substrate
Effects of lift-off and strain relaxation on optical properties of InGaN/GaN blue LED grown on 150 mm diameter Si (111) substrate

Highlights

 

•InGaN/GaN blue LED has been grown on 150-mm diameter Si (111) substrate by MOCVD.

•GaN-on-Si blue LED has been lifted-off by mechanical thinning and chemical etching.

•The lift-off resulted in phonons softening of GaN in the LED structure.

•The PL decay of the InGaN/GaN blue LED is accelerated by the lift-off.

•Both are related to the lift-off induced strain relaxations and redistribution.

We report on the effect of strain relaxations induced by lift-off in an InGaN/GaN multiple quantum wells (MQWs) blue light-emitting diode (LED) structure grown by metal-organic chemical vapor deposition (MOCVD) on a 150-mm diameter Si (111) substrate. To manage the lattice strain and, meanwhile, filter the threading dislocations, an AlN nucleation layer followed by a fourfold-step-graded AlGaN buffer together with multiple low-temperature AlN interlayers hasbeen employed, which results in a crack-free growth of 4.9-µm GaN on Si (111) in the studied LED structure. High-resolution x-ray diffraction (HRXRD) and micro-Raman spectroscopy reveal that MQWs are coherently grown on the GaN layer while the GaN layer is tensile strained on the Si (111) substrate. Lift-off by wet-chemical etching results in phonon softening of both the top-layer GaN and the InGaN within the QWs; meanwhile, a red-shift of ~11 meV in the photoluminescence (PL) from the MQWs accompanied by a significant decrease (>4.9 times) in the PL-peak decay time is observed at room temperature. These observations are discussed and associated with the lift-off induced strain relaxations, which change the wafer curvature that in turn results in redistribution of in-plane stresses along the growth direction in the GaN-on-Si LED structure.

Keywords:  A1. Characterization;  A1. High-resolution x-ray diffraction;  A3. MOCVD;  B.1 GaN-on-Si;   B1. InGaN/GaN blue LED

Source: Sciencedirect

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