Comparison of nonpolar III-nitride vertical-cavity surface-emitting lasers with tunnel junction and ITO intracavity contacts

We report on the lasing of III-nitride nonpolar, violet, vertical-cavity surface-emitting lasers (VCSELs) with III-nitride tunnel-junction (TJ) intracavity contacts and ion implanted apertures (IIAs). The TJ VCSELs are compared to similar VCSELs with tin-doped indium oxide (ITO) intracavity contacts. Prior to analyzing device results, we consider the relative advantages of III-nitride TJs for blue and green emitting VCSELs. The TJs are shown to be most advantageous for violet and UV VCSELs, operating near or above the absorption edge for ITO, as they significantly reduce the total internal loss in the cavity. However, for longer wavelength III-nitride VCSELs, TJs primarily offer the advantage of improved cavity design flexibility, allowing one to make the p-side thicker using a thick n-type III-nitride TJ intracavity contact. This offers improved lateral current spreading and lower loss, compare to using ITO and p-GaN, respectively. These aspects are particularly important for achieving high-power CW VCSELs, making TJs the ideal intracavity contact for any III-nitride VCSEL. A brief overview of III-nitride TJ growth methods is also given, highlighting the molecular-beam epitaxy (MBE) technique used here. Following this overview, we compare 12 mu m aperture diameter, violet emitting, TJ and ITO VCSEL experimental results, which demonstrate the significant improvement in differential efficiency and peak power resulting from the reduced loss in the TJ design. Specifically, the TJ VCSEL shows a peak power of similar to 550 mu W with a threshold current density of similar to 3.5 kA/cm(2), while the ITO VCSELs show peak powers of similar to 80 mu W and threshold current densities of similar to 7 kA/cm

Citation

Leonard JT, Young EC, Yonkee BP, Cohen DA, Shen C, et al. (2016) Comparison of nonpolar III-nitride vertical-cavity surface-emitting lasers with tunnel junction and ITO intracavity contacts. Gallium Nitride Materials and Devices XI. Available: http://dx.doi.org/10.1117/12.2206211.

Sponsors

The authors would like to thank Mitsubishi Chemical Corporation for providing high-quality free-standing mplane GaN substrates. This work was funded in part by the King Abdulaziz City for Science and Technology (KACST) Technology Innovations Center (TIC) program, and the Solid State Lighting and Energy Electronics Center (SSLEEC) at the University of California, Santa Barbara (UCSB). Partial funding for this work came from Prof. Boon S. Ooi at King Abdullah University of Science and Technology (KAUST), through his participation in the KACST-TIC program. A portion of this work was done in the UCSB nanofabrication facility, with support from the NSF NNIN network (ECS- 03357650), the UCSB Materials Research Laboratory (MRL), which is supported by the NSF MRSEC program (DMR- 1121053), and the California NanoSystem Institute’s (CNSIs) Center for Scientific Computing at UCSB.