Quantum Well Transverse Junction Stripe Laser.

The research and development of four new quantum well transverse junction stripe lasers (TJS) are presented, which are (1) GaAs-AlGaAs multiple quantum well (MQW) TJS laser; (2) GaAs-AlGaAs single quantum well (SQW) TJS laser; (3) InGaAs-GaAs-AlGaAs strained layer MQW-TJS laser; and (4) InGaAs-GaAs-AlGaAs strained-layer SQW-TJS laser. The research work involves (1) crystal growth and material characterization, (2) laser diode fabrication and device testing. The first (CW, 300K) MQW-TJS laser with a lateral heterobarrier produced by selective zinc diffusion disordering has been demonstrated. The low threshold current of 25mA and single mode operation have demonstrated that high quality p^+-p-n junction and disordered heterobarrier can be fabricated by zinc diffusion disordering. The laser threshold is improved by a factor of 3 compared to a conventional homojunction TJS laser processed simultaneously. This threshold improvement is attributed to the introduction of a lateral disordered heterobarrier to reduce the threshold current density. The first (CW, 300K) strained-layer InGaAs-GaAs -AlGaAs MQW-TJS laser has also been developed. The laser diode operates single mode at 21mA. This excellent performance of low threshold and single mode operation have demonstrated that high quality of the pseudomorphic layer and a lateral p^+-p-n junction can be formed by zinc diffusion disordering of InGaAs-GaAs-AlGaAs strained -layers. This result also indicates that the zinc diffusion has general property of induced disordering of both unstrained and strained superlattices, which is of importance for devices design and fabrication. Both SQW-TJS and strained-layer SQW-TJS lasers have been demonstrated. The threshold currents of these lasers are 105mA and 55mA respectively, which are higher than those of MQW-TJS and strained-layer MQW-TJS laser. This results may indicate the MQW active region is superior to the SQW active region for the TJS laser operation. However, the first (CW, 300K) strained-layer SQW-TJS laser with I_{rm th} of 55mA has been achieved. Given that the development of SQW-TJS laser is still in the early stage, these results show that SQW-TJS lasers are very promising for low threshold laser operation.