Smooth e-beam-deposited tin-doped indium oxide for III-nitride vertical-cavity surface-emitting laser intracavity contacts
AuthorsLeonard, J. T.
Cohen, D. A.
Yonkee, B. P.
Farrell, R. M.
DenBaars, S. P.
Speck, J. S.
Permanent link to this recordhttp://hdl.handle.net/10754/673073
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AbstractWe carried out a series of simulations analyzing the dependence of mirror reflectance, threshold current density, and differential efficiency on the scattering loss caused by the roughness of tin-doped indium oxide (ITO) intracavity contacts for 405 nm flip-chip III-nitride vertical-cavity surface-emitting lasers (VCSELs). From these results, we determined that the ITO root-mean-square (RMS) roughness should be <1 nm to minimize scattering losses in VCSELs. Motivated by this requirement, we investigated the surface morphology and optoelectronic properties of electron-beam (e-beam) evaporated ITO films, as a function of substrate temperature and oxygen flow and pressure. The transparency and conductivity were seen to increase with increasing temperature. Decreasing the oxygen flow and pressure resulted in an increase in the transparency and resistivity. Neither the temperature, nor oxygen flow and pressure series on single-layer ITO films resulted in highly transparent and conductive films with <1 nm RMS roughness. To achieve <1 nm RMS roughness with good optoelectronic properties, a multi-layer ITO film was developed, utilizing a two-step temperature scheme. The optimized multi-layer ITO films had an RMS roughness of <1 nm, along with a high transparency (∼90% at 405 nm) and low resistivity (∼2 × 10-4 Ω-cm). This multi-layer ITO e-beam deposition technique is expected to prevent p-GaN plasma damage, typically observed in sputtered ITO films on p-GaN, while simultaneously reducing the threshold current density and increasing the differential efficiency of III-nitride VCSELs.
CitationLeonard, J. T., Cohen, D. A., Yonkee, B. P., Farrell, R. M., DenBaars, S. P., Speck, J. S., & Nakamura, S. (2015). Smooth e-beam-deposited tin-doped indium oxide for III-nitride vertical-cavity surface-emitting laser intracavity contacts. Journal of Applied Physics, 118(14), 145304. doi:10.1063/1.4931883
SponsorsThe authors would like to thank Mitsubishi Chemical Corporation for providing high-quality free-standing m-plane GaN substrates, Tony Bosch at the UCSB Nanofabrication facility for e-beam system support, Nina Hong at J. Woollam for ellipsometer modeling expertise, and Daniel F. Feezell at the University of New Mexico for general discussions on VCSELs. 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 Professor 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), as well as the UCSB Materials Research Laboratory (MRL), which is supported by the NSF MRSEC program (DMR-1121053).
PublisherAMER INST PHYSICS
JournalJOURNAL OF APPLIED PHYSICS