Optical pump–terahertz probe study of HR GaAs:Cr and SI GaAs:El2 structures with long charge carrier lifetimes

The time dynamics of nonequilibrium charge carrier relaxation processes in SI GaAs:EL2 (semi-insulating gallium arsenide compensated with EL2 centers) and HR GaAs:Cr (high-resistive gallium arsenide compensated with chromium) were studied by the optical pump–terahertz probe technique. Charge carrier lifetimes and contributions from various recombination mechanisms were determined at different injection levels using the model, which takes into account the influence of surface and volume Shockley–Read–Hall (SRH) recombination, interband radiative transitions and interband and trap-assisted Auger recombination. It was found that, in most cases for HR GaAs:Cr and SI GaAs:EL2, Auger recombination mechanisms make the largest contribution to the recombination rate of nonequilibrium charge carriers at injection levels above ~(0.5–3)·1018 cm−3, typical of pump–probe experiments. At a lower photogenerated charge carrier concentration, the SRH recombination prevails. The derived charge carrier lifetimes, due to the SRH recombination, are approximately 1.5 and 25 ns in HR GaAs:Cr and SI GaAs:EL2, respectively. These values are closer to but still lower than the values determined by photoluminescence decay or charge collection efficiency measurements at low injection levels. The obtained results indicate the importance of a proper experimental data analysis when applying terahertz time-resolved spectroscopy to the determination of charge carrier lifetimes in semiconductor crystals intended for the fabrication of devices working at lower injection levels than those at measurements by the optical pump–terahertz probe technique. It was found that the charge carrier lifetime in HR GaAs:Cr is lower than that in SI GaAs:EL2 at injection levels > 1016 cm−3.В ст. ошибочно: Irina A. Kolesnikov

Effect of gallium arsenide charge carrier life time on the generation and detection efficiency of continuous and pulsed terahertz radiation

A configuration and test samples of photoconductive dipole antennas based on SI-GaAs:Cr and LT-GaAs for generation and detection of terahertz radiation are developed. Their operating characteristics in the pulsed mode and in the mode of operation as photomixers are experimentally investigated

Influence of split-ring resonators on the terahertz transmission of a planar waveguide

Terahertz transmission spectra of subwavelength split-ring resonator structures on ceramic substrates are investigated experimentally. For terahertz wave propagation along the ring resonators used as one of the faces of a planar dielectric waveguide, enhanced transmission is detected near the LC-resonance frequency. Dependences of the resonant absorption frequencies on the geometric structure characteristics are found for normal terahertz wave propagation through the structures

Properties of gallium oxide films obtained by HF-magnetron sputtering

The results of an analysis of structure and phase composition of gallium oxide films obtained by HF-magnetron sputtering are presented. It is shown that in the interval 290–350 K, the increase in the film conductivity with increasing temperature is due to the excitation of electrons from a local level Е t located 0.95 eV below the conduction band bottom

Influence of split-ring resonators on the terahertz transmission of a planar waveguide

Terahertz transmission spectra of subwavelength split-ring resonator structures on ceramic substrates are investigated experimentally. For terahertz wave propagation along the ring resonators used as one of the faces of a planar dielectric waveguide, enhanced transmission is detected near the LC-resonance frequency. Dependences of the resonant absorption frequencies on the geometric structure characteristics are found for normal terahertz wave propagation through the structures

Properties of gallium oxide films obtained by HF-magnetron sputtering

The results of an analysis of structure and phase composition of gallium oxide films obtained by HF-magnetron sputtering are presented. It is shown that in the interval 290–350 K, the increase in the film conductivity with increasing temperature is due to the excitation of electrons from a local level Е t located 0.95 eV below the conduction band bottom

Dependence of X-ray sensitivity of GaAs:Cr sensors on material of contacts

The investigation of the pulse height distribution and X-ray sensitivity depending on the contact material on high resistive chromium compensated gallium arsenide (HR GaAs:Cr) sensors is presented. Some samples had Cr/Ni contacts made using electron-beam deposition and some samples had In additionally alloyed into the contacts. Three different configuration of sensors were investigated: Ni/Cr - HR GaAs:Cr – Cr/Ni, In/Ni/Cr - HR GaAs:Cr – Cr/Ni/In and In/Ni/Cr - HR GaAs:Cr – Cr/Ni. Depending on the type of sensor there are differences in both the X-ray sensitivity and pulse height distribution depending on X-ray intensity. Ni/Cr - HR GaAs:Cr – Cr/Ni – structures have shown sublinear sensitivity dependence to intensity, while In/Ni/Cr - HR GaAs:Cr – Cr/Ni/In are characterized by superlinear dependence holding everything else constant. The results and possible causes are discussed in this paper