Visible (670 nm) vertical cavity surface emitting lasers with indium tin oxide transparent conducting top contacts

Abstract

One significant performance limiting parameter for top-surface emitting red VCSELs is the need for a top contacting surface which is both highly conducting and non-absorbing at the optical emission wavelength. The GaAs cap layer typically deposited on longer wavelength structures to facilitate contacting is strongly absorbing at 670 nm unless restricted to a thickness of only several nanometers. This compromises both the quality of the ohmic contact and the level of lateral conductivity achievable in red VCSEL structures which rely on lateral current flow for current injection. In this paper we report the use of indium tin oxide (ITO) as a transparent top surface contact for red VCSELs, resulting in substantial improvements in both turn on voltage and power output in these devices.