OMVPE growth of highly strain-balanced GaInAs/AlInAs/InP for quantum cascade lasers

Abstract

The growth and characterization of highly strain-balanced (SB) GaInAs/AlInAs/InP quantum-well heterostructures for mid-infrared quantum cascade lasers (QCLs) are reported. Growth conditions were established to provide a step-flow growth mode, which is believed to be important for precise thickness control of the ultrathin (∼1 nm) epilayers of the injector/active QCL regions. Heterostructures with GaInAs and AlInAs absolute layer strain ranging from 0.5% to as high as 1.5% were grown by organometallic vapor-phase epitaxy at a growth temperature of 580 °C and utilized tertiarybutyl arsine and tertiarybutyl phospine as group V sources and triethylgallium, trimethylindium, and trimethylaluminum as group III sources. Growth was optimized by characterization of SB GaInAs/AlInAs/InP multiple quantum-well structures using high-resolution X-ray diffraction (XRD) and atomic force microscopy. Similar surface step structure and XRD spectra were obtained over the 0.5–1.5% SB range. QCLs with nominal strain balance of 1% and based on a four-quantum-well double-phonon resonance-active region design were grown and processed as ridge lasers. These lasers operate at 4.8 μm in pulsed mode at room temperature with a threshold current density of 1.3 kA/cm 2, peak power of 1.74 W, and power-conversion efficiency of 9.7%. These results are comparable to state-of-the-art QCLs grown by molecular beam epitaxy.