Laser threshold and optical gain of blue optically pumped InGaN/GaN multiple quantum wells (MQW) grown on Si

Abstract

AbstractOptical and laser properties of a series of MQW heterostructures with varying geometry grown on silicon with Al predeposition were investigated. Photoluminescence (PL) band positions covered a spectral range of 430 – 460 nm under Iexc=1 MW/cm2 and 445‐505 nm under Iexc=0.15 W/cm2. Laser action was achieved under transversal optical pumping at room temperature using only cleaved lateral facets of the samples as laser mirrors. The laser threshold rose from 137 kW/cm2 to 300 kW/cm2 with laser wavelength increase from 440 nm to 465 nm. Numerical simulation of the laser conditions shows that the minimal threshold is realized on the fifth order mode. However, the calculated value of material optical gain of InGaN at the laser threshold increases only from 750 cm–1 to 1020 cm–1, mainly due to absorption rise in the substrate with increasing wavelength. Correlation was observed between PL characteristics and laser threshold. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)