We have fabricated GaN-based light-emitting diodes using transparent indium tin oxide (ITO) p contacts. ITO-contacted devices required an additional 2 V to drive 10 mA, as compared to similar devices with metal contacts. However, ITO has lower optical absorption at 420 nm (α=664 cm−1) than commonly used thin metal films (α=3×105 cm−1). Uniform luminescence was observed in ITO-contacted devices, indicating effective hole injection and current spreading.

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It is demonstrated that placing an n-type Te δ doping aside a single strained quantum well (QW) is an efficient way to control the initial carrier concentration in the QW and thus to lower transparency current density, Jtr, while preserving low internal losses. This is in contrast with uniform doping of the active area. Jtr of 11.3 A/cm<thin>2 and threshold current density of 54.4 A/cm2, which are both the lowest values reported to date for strained InxGa1−xAs/GaAs semiconductor lasers, were obtained. A somewhat higher injection efficiency is obtained when the energy levels are adjusted so that the electrons tunnel from the delta well directly into the QW.

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It is demonstrated that the incorporation of Te n-type δ doping close to a single-strained InGaAs/GaAs quantum well improves the temperature stability of the laser, as indicated by the higher characteristic temperature and by the reduced sensitivity of the threshold current to temperature variations. This improvement results from the strong coupling between the quantum well and the δ-doping well.