Facile and Electrically Reliable Electroplated Gold Contacts to p-Type InAsSb Bulk-Like Epilayers.

Sebastian Złotnik,Jerzy Wróbel,Jarosław Wróbel,Marek Andrzej Kojdecki,Małgorzata Nyga,Jacek Boguski

doi:10.3390/s21165272

Abstract

Narrow band-gap semiconductors, namely ternary InAsSb alloys, find substantial technological importance for mid-infrared application as photodetectors in medical diagnostics or environmental monitoring. Thus, it is crucial to develop electrical contacts for these materials because they are the fundamental blocks of all semiconductor devices. This study demonstrates that electroplated gold contacts can be considered as a simple and reliable metallization technology for the electrical-response examination of a test structure. Unalloyed electroplated Au contacts to InAsSb exhibit specific contact resistivity even lower than vacuum-deposited standard Ti–Au. Moreover, temperature-dependent transport properties, such as Hall carrier concentration and mobility, show similar trends, with a minor shift in the transition temperature. It can be associated with a difference in metallization technology, mainly the presence of a Ti interlayer in vacuum-deposited contacts. Such a transition may give insight into not only the gentle balance changes between conductivity channels but also an impression of changing the dominance of carrier type from p- to n-type. The magnetotransport experiments assisted with mobility spectrum analysis clearly show that such an interpretation is incorrect. InAsSb layers are strongly p-type dominant, with a clear contribution from valence band carriers observed at the whole analyzed temperature range. Furthermore, the presence of thermally activated band electrons is detected at temperatures higher than 220 K.

Highlights

Carrier injection from an electrode to a semiconductor medium has routinely been a central issue in any common optoelectronic device
Metallization acting as electrical contacts to narrow band-gap (NBG) semiconductors is an integral part of devices based on such materials and determines device performances and their reliability
Photodetectors composed of InAsSb are under constant expansion on a market, requiring device processing for electrical characterization with a rather simple and fast metallization methodology

Summary

Introduction

Carrier injection from an electrode to a semiconductor medium has routinely been a central issue in any common optoelectronic device. Among the AIII – BV NBG semiconductors are arsenides (e.g., InAs and GaAs) and antimonides (e.g., InSb and GaSb) as well as their ternary alloys (e.g., InAs1−x Sbx ), considered as crucial materials for mid-infrared (MIR) optoelectronic devices, operating with a radiation of wavelength between 2 and 14 μm [1]. The substitution of antimony sites in InSb with isovalent arsenic reduces the energy gap of an InAsSb solid solution to a value lower than the energy gap of their constituent binary compounds, being the ternary alloy with the lowest energy gap among the AIII –BV semiconductors [2]. The development of InAsSb alloys led to replacing HgCdTe in MIR applications due to superior bond strengths, material stability, doping capability or high-quality AIII –BV substrates [2]. InAsSb-based detector technology has been extended to the development of photodiodes with a variety of configurations such as n-i-p structure [3,4] or to the XBn barrier structures [7]

Methods

Results

Conclusion