Observation of persistent photoconductivity in bulk gallium arsenide and gallium phosphide samples at cryogenic temperatures using the whispering gallery mode method

Abstract

Whispering Gallery modes in bulk cylindrical Gallium Arsenide and Gallium Phosphide samples have been examined both in darkness and under white light at cryogenics temperatures ≤ 50 K.In both cases persistent photoconductivity was observed after initially exposing semiconductors to white light from a halogen lamp. Photoconductance decay time constants for GaP and GaAs were determined to be 0.900 ± 0.081 ns and 1.098 ± 0.063 ns, respectively, using this method.

Contactless methods of conductivity and sheet resistance measurement for semiconductors, conductors and superconductors

“…Using this technique, the persistent conductivity of a bulk GaAs sample was measured [26]. The results of these measurements are shown in figure 8(a).…”

Detrapping and retrapping of free carriers in nominally pure single crystal GaP, GaAs, and 4H–SiC semiconductors under light illumination at cryogenic temperatures

“…High-purity non-doped single-crystal semiconductor cylinders of GaP (48.1 mm diameter and 5 mm height), GaAs (25.4 mm diameter and 6.3 mm height) and 4H-SiC (11 mm diameter and 2.62 mm height) were placed in silver-plated copper cavities (see Fig. 1; individual cavity dimensions were chosen to suit the semiconductor sample under examination 7,8,16 ) located in a vacuum chamber and cooled using a 35 K single-stage cryocooler.…”

“…Since 1977, many experiments have been performed in order to study the effects of light on semiconductors such as Zn 0.02 Cd 0.98 Te, 1,2 AlAs/GaAs, 3 XAs:Si, 4 AlGaN/GaN, 5 Al x Ga 1−x C 60 , 6 gallium phosphide (GaP) and gallium arsenide (GaAs). 7,8 Those experiments showed changes in the microwave properties of the semiconductors under light illumination and persistence of photoconductivity after the illumination was terminated.…”

“…Previously we presented the results of measurements of gallium phosphide and gallium arsenide under illumination using the very sensitive "whispering gallery mode" method. 7,8 The whispering gallery mode technique used on these samples is able to resolve changes in microwave permittivity and losses of the order of a few parts per million. That allowed us to precisely determined the time constants for the trapping and detrapping rates in gallium phosphide and gallium arsenide under white light illumination.…”

Electromagnetic properties of polycrystalline diamond from 35 K to room temperature and microwave to terahertz frequencies

“…[12][13][14] The technique uses higher order hybrid modes excited in a cylindrical or spherical dielectric. The WGM technique is especially useful for measurements of extremely low-loss materials at both cryogenic 15,16 and room temperature. The relationship between resonant frequencies dimensions of the resonant cavity, and permittivity of the sample under test is calculated with a rigorous electromagnetic simulation software based on the method of lines (MoL) 17 with an accuracy better than 10 -4 .…”