Investigation of Zn diffusion by SIMS and its effects on the performance of AlGaInP-based red lasers
The behaviour of Zn diffusion in a GaInP/(Al0.5Ga0.5)0.5In0.5P multiple quantum-well (MQW) layer was investigated as a function of the growth temperature and Zn/III ratio by secondary ion mass spectroscopy (SIMS). Then the diffusion length of Zn in the undoped (Al0.7Ga0.3)0.5In0.5P layer from the Zn-doped (Al0.7Ga0.3)0.5In0.5P (Zn: 1.0–1.2 × 1018 cm−3) cladding layer was evaluated to design a barrier layer for Zn diffusion into the GaInP/(Al0.5Ga0.5)0.5In0.5P MQW active layer. As a result of incorporating a 130 nm thick diffusion barrier on top of the MQW layers of the AlGaInP red laser, the full width at half maximum (FWHM) of the photoluminescence (PL) spectrum for the GaInP/(Al0.5Ga0.5)0.5In0.5P MQW layers was reduced from 60 meV to 30 meV at room temperature (RT), and the threshold current was also greatly reduced from 110 mA to 75 mA for a standard AlGaInP-based ridge laser as compared to a AlGaInP laser without a diffusion barrier.