Influence of base material thickness on spectrometry of semiconductor detectors based on semi-insulating GaAs

¹ Institute of Nuclear and Physical Engineering, Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, SK-812 19 Bratislava, Slovak Republic
² Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, SK-814 04 Bratislava, Slovak Republic

^* andrea.sagatova@stuba.sk

Published online: 21 November 2023

Abstract

The bulk semi-insulating GaAs material was used for preparation of pad radiation detectors with circular contacts of 1 mm diameter. The spectrometric properties of a semiconductor detector depend on the quality of the base material and on the deposited metallization. Another factor affecting the detector spectrometry is the applied bias controlling the electric collection field. With increasing bias, the charge collection efficiency of particular detector grows. However, this spectrometric property should be changing with detector thickness, which affects the intensity of electric collection field at constant bias applied through the detector sandwich structure. In this paper we have studied the electrical and spectrometric properties of semi-insulating GaAs detectors as a function of their thickness. The measured saturation reverse current was in the range of 3 – 30 nA, increasing with decreasing detector thickness at a substrate resistivity of about of 10⁷ Ωcm. The maximal obtainable charge collection efficiency evaluated from ²⁴¹Am gamma spectra grew with decreasing detector thickness from 50% for a 450 µm thick detector to 80% for a 230 µm thick detector.