Demonstration of a Ⅲ-nitride vertical-cavity surface-emitting laser with a Ⅲ-nitride tunnel junction intracavity contact

摘要

We report on a Ⅲ-nitride vertical-cavity surface-emitting laser (VCSEL) with a Ⅲ-nitride tunnel junction (TJ) intracavity contact. The violet nonpolar VCSEL employing the TJ is compared to an equivalent VCSEL with a tin-doped indium oxide (ITO) intracavity contact. The TJ VCSEL shows a threshold current density (J_(th)) of ～3.5 kA/cm~2, compared to the ITO VCSEL J_(th) of 8 kA/cm~2. The differential efficiency of the TJ VCSEL is also observed to be significantly higher than that of the ITO VCSEL, reaching a peak power of ～550μW, compared to ～80μW for the ITO VCSEL. Both VCSELs display filamentary lasing in the current aperture, which we believe to be predominantly a result of local variations in contact resistance, which may induce local variations in refractive index and free carrier absorption. Beyond the analyses of the lasing characteristics, we discuss the molecular-beam epitaxy (MBE) regrowth of the TJ, as well as its unexpected performance based on band-diagram simulations. Furthermore, we investigate the intrinsic advantages of using a TJ intracavity contact in a VCSEL using a 1D mode profile analysis to approximate the threshold modal gain and general loss contributions in the TJ and ITO VCSEL.