Evaluation of performance capabilities of emitters and detectors based on a common MQW structure

Photodetectors (PDs) based on three separate confinement-multiple quantum well (SCH–MQW) structures (with 2, 4 and 8 QWs) and six graded-index (GRIN) SCH–MQW structures were studied for two types of devices: guided wave and non-guided wave devices. Non-guided wave devices were processed and the capacitance and the responsivity, in the wavelength range of 750–900 nm, were determined for various bias voltages. Guided wave PDs were simulated using the transfer matrix method for optical mode calculation and the minimum length of the detectors was calculated for absorbing 99% of the incident light. The junction capacitance of the guided wave PDs was calculated from the measured capacitance of non-guided wave devices and the minimum size of the devices; values of 215, 101, and 52 fF were obtained for 2, 4 and 8 QW SCH–MQW structures. Laser diodes were also fabricated from the three different SCH–MQW structures. Threshold current densities (Jth) of 737, 755 and 1210 A cm−2 were measured for 2, 4 and 8 QWs, respectively. Further improvement was achieved using GRINSCH–MQW structures and LDs with 4 QWs exhibited 33% decrease in Jth and 22% increase in slope efficiency.