GdN Nanoisland-Based GaN Tunnel Junctions

TL;DR

This paper demonstrates that GdN nanoislands significantly improve inter-band tunneling in GaN junctions, enabling low-resistance, low-absorption tunnel contacts for optoelectronic devices and allowing novel heterostructure designs.

Contribution

It introduces GdN nanoislands as a means to enhance tunneling in GaN, enabling new device architectures not possible with planar epitaxy.

Findings

GdN nanoislands increase tunneling by several orders of magnitude.

Tunnel junctions exhibit low specific resistivity (1.3 x 10^-3 Ω·cm^2).

Strong electroluminescence observed at 20K in tunneling GaN p-n junctions.

Abstract

We show that GdN nanoislands can enhance inter-band tunneling in GaN PN junctions by several orders of magnitude, enabling low optical absorption low-resistance tunnel junctions (specific resistivity 1.3 X 10-3 {\Omega}-cm2) for various optoelectronic applications. We exploit the ability to overgrow high quality GaN over GdN nanoislands to create new nanoscale heterostructure designs that are not feasible in planar epitaxy. GdN nanoisland assisted inter-band tunneling was found to enhance tunneling in both of the polar orientations of GaN. Tunnel injection of holes was confirmed by low temperature operation of GaN p-n junction with a tunneling contact layer, showing strong electroluminescence down to 20K. The availability of tunnel junctions with negligible absorption could not only improve the efficiency of existing optoelectronic devices significantly, but also enable new electronic and optical devices based on wide band gap materials.