Technology development of 3-S GaAs radiation detectors

Meikle, Andrew R. (1999) Technology development of 3-S GaAs radiation detectors. MSc(R) thesis, University of Glasgow.

Abstract

A novel type of GaAs radiation detector featuring a three-dimensional array of electrodes that penetrate through the detector bulk is described. The development of the technology to fabricate such a detector is presented along with electrical and radiation source tests. Simulations of the electrical characteristics are given for detectors of various dimensions. Laser drilling was used to create holes in the detector bulk. Two types of laser were investigated: Nd:YAG and Ti: Sapphire. The Nd:YAG laser produced repeatable round holes of 30 mum diameter with little or no taper and smooth internal walls. The Ti:Sapphire laser produced holes of 100 mum diameter with very little ejected debris. Electrodes were formed within the holes by metal evaporation, creating diode cells with a Schottky-Schottky configuration. Two types of cell were fabricated: three-electrode and nine-electrode. The cells had 60 mum diameter holes with a 210 mum pitch. Electrical measurements made on both cells revealed characteristics with low leakage currents and high breakdown voltages. The three-electrode cell had a reverse breakdown voltage of approximately 100 V and a reverse leakage current of approximately 20 nA while the nine-electrode cell had a reverse breakdown voltage of approximately 500 V and a reverse leakage current of approximately 5 nA. Forward and reverse bias I-V measurements showed asymmetrical characteristics, which are not seen in planar diodes. Energy spectra were obtained using 5.45 MeV alpha particles and 60 keV photons. The alpha source measurements produced a charge collection efficiency of 50%. Simulations of a nine-electrode cell with identical dimensions to the fabricated cell were performed. The results showed asymmetrical forward and reverse bias I-V characteristics, similar to those found experimentally. The simulated I-V characteristics also showed a breakdown voltage of 500 V with low leakage currents, consistent with those found experimentally. The simulations showed that the cell is not fully depleted at 500 V. Simulations of a nine-electrode cell with 10 mum electrodes with a 25 mum pitch were also performed. The I-V characteristics again showed a high breakdown voltage with a low leakage current but also showed a full depletion voltage of just 8 V.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Keywords: Electrical engineering.
• Colleges/Schools: College of Science and Engineering
• Supervisor's Name: Smith, Ken and Marsh, John
• Date of Award: 1999
• Depositing User: Enlighten Team
• Unique ID: glathesis:1999-71986
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 17 May 2019 13:31
• Last Modified: 11 Aug 2021 09:00
• URI: https://theses.gla.ac.uk/id/eprint/71986