Optimization of In‐Reactor In Situ Activation Annealing Conditions for Tunnel Junction Layers in Multiquantum Shell GaN‐Based Devices

Abstract

For realizing room‐temperature continuous‐wave operation in core–shell GaN nanowire‐based semiconductor lasers, certain device characteristics are required, namely, a low threshold current and low operating voltage. To reduce the operating voltage and inject current into the m‐plane multiquantum shell (MQS) active region, a new structure with a tunnel junction and embedded n‐GaN is proposed. One of the problems in this proposed device architecture is the high resistance at the tunnel junction layer due to hydrogen passivation in the insufficiently activated p‐GaN shell. In situ activation annealing and suppression of re‐passivation during subsequent growth are necessary to reduce the operating voltage. Herein, the time and temperature dependence of in situ activation annealing in a reactor to lower the resistance of tunnel junction layers grown on nanowires with nonpolar m‐planes is investigated. Subsequent n+‐GaN growth is implemented at 550 °C. As a result, the turn‐on voltage is observed to be dependent on the activation annealing time and temperature. The lowest turn‐on voltage is ≈5.4 V at an activation annealing time of 30 min and activation annealing temperature of 800 °C.