ELECTRICAL CHARACTERISTICS OF PROTON-IMPLANTED VERTICAL-CAVITY SURFACE-EMITTING LASERS

The electrical characteristics of proton-implanted GaAs quantum-well v ertical-cavity surface-emitting semiconductor lasers (VCSEL's) have be en studied. We show that the 2kT current, observed over many decades i n these VCSEL's, is primarily due to nonradiative recombination mechan isms. These include surface recombination at the edges of the proton-i mplanted region and bulk recombination at defects and heterojunction i nterface traps. The contribution of these mechanisms to the total nonr adiative current and the threshold current density has been calculated . Lateral spontaneous emission measurements have been used to prove th at the radiative current has a kT behavior in the subthreshold region. Electrical derivative measurements have been used to identify leakage current paths through the proton-implanted region in the low-bias reg ions. In addition, electrical derivative measurements have been used t o measure the variation of series resistance with current near the las ing threshold. From a consideration of the various current paths in th e VCSEL, a lumped circuit equivalent model for the VCSEL has been deve loped.