Comparison of ultraviolet APDs grown on free-standing GaN and sapphire substrates

Abstract

There is a need for semiconductor-based ultraviolet photodetectors to support avalanche gain in order to realize better performance andmore effective compete with existing technologies. Wide bandgap III-Nitride semiconductors are the promising material system for the development of avalanche photodiodes (APDs) that could be a viable alternative to current bulky UV detectors such as photomultiplier tubes. In this paper, we review the current state-of-the-art in IIINitride visible-blind APDs, and present our latest results on GaN APDs grown on both conventional sapphire and low dislocation density free-standing c-and m-plane GaN substrates. Leakage current, gain, and single photon detection efficiency (SPDE) of these APDs were compared. The spectral response and Geiger-mode photon counting performance of UV APDs are studied under low photon fluxes, with single photon detection capabilities as much as 30% being demonstrated in smaller devices. Geiger-mode operation conditions are optimized for enhanced SPDE.

Temperature dependence of the dark current and activation energy at avalanche onset of a GaN avalanche photodiodes

“…These defects are believed to be caused by a lattice mismatch between the grown material and the substrate. Recent studies indicate that growing GaN on bulk GaN helps, 12,15 but that further improvement is needed. This improvement can be achieved by lateral epitaxial overgrowth (LEO) or a modification of LEO that uses nano-columns as a method of breaking up threading dislocation defects.…”

“…The crux of the matter is that for room temperature operation, the APDs we have made require that we reject approximately 50% of the detected photon events if we want to accept only photo-induced counts, 8,12,14,15 i.e. reject effectively all dark induced counts.…”

Reduction of threading dislocation density in top-down fabricated GaN nanocolumns via their lateral overgrowth by MOCVD

“…Film growth on substrates such as silicon and sapphire is the most common device preparation method [5,6], with the aim of producing transistors with high electron mobility. However, a key issue with the growth of these films is the presence of threading dislocations (TDs), a concern when fabricating GaN-based semiconductor devices due to the negative effects they may have on device quality such as increased current leakage [7,8], decreased efficiency and lifetime [9], disrupted electric field distribution and a premature breakdown due to microplasmas [10,11]. Dislocation densities in the range of 10 8 cm −2 to 10 10 cm −2 are often recorded for few-to-several micrometer-thick heteroepitaxially grown GaN films [12,13].…”

“…Dislocation densities in the range of 10 8 cm −2 to 10 10 cm −2 are often recorded for few-to-several micrometer-thick heteroepitaxially grown GaN films [12,13]. While light emitting diodes, which only need to operate in forward bias, may be fabricated from material with such high TD densities (TDDs) [10,14], for high power or high temperature applications it is imperative that TDD should be considerably reduced to produce quality devices.…”

Detection of VUV Light with Avalanche Photodiodes

“…On the other hand, they present some advantages, namely the lower biasing voltages, higher gains with lower leak currents, the solar blind capability. Recent reviews on these APDs can be found in [11][12][13][14][15][16][17] and references therein. Through the last decade, we have investigated the response characteristics of a large area APD from API to the scintillation VUV light produced in gaseous argon and xenon at room temperature [4,5].…”