Effect of the carbon acceptor concentration on the photoquenching and following enhancement of the photoacoustic signals of semi-insulating GaAs

Abstract

Investigation of the annealing effect on the nonradiative carrier recombination in AlGaAs/GaAs utilizing the piezoelectric photothermal technique Rev. Sci. Instrum. 74, 550 (2003); 10.1063/1.1515888Lattice relaxation and metastability of the EL2 defect in semi-insulating GaAs and low temperature GaAsThe spectral and the time dependent piezoelectric photoacoustic ͑PPA͒ measurements under the continuous light illumination were carried out at 85 K to investigate nonradiative recombination processes involving EL2 defect levels in carbon concentration controlled and not intentionally doped semi-insulating ͑SI͒ GaAs. The decrease of the PPA signal due to the photoquenching effect of EL2 is observed for a short period of illumination in the photon energy region from 1.0 to 1.3 eV. Since almost all of the carbon acceptors are compensated by deep donor EL2 in SI GaAs, electron occupancy of EL2 level can be controlled by changing the carbon acceptor concentration. It is found that the photoquenching becomes drastic with increasing the carbon concentration. After fully photoquenching, the PPA signal increases again through a local minimum by the continuous light illumination and finally exceeds the initial value before illumination until the saturation level is reached. The deep donor level EL6 and its metastable state are proposed. EL6 level donates electrons to compensate a part of carbon acceptors after EL2 0 to EL2* transition is accomplished. The nonradiative recombination through this level generates the PPA signal. Since the PPA measurement can detect lower concentration of EL6 than that of EL2, the higher sensitivity of the PPA measurements than the optical absorption measurements is pointed out. The usefulness of the PPA technique for studying the nonradiative transition through deep levels in semiconductors is also suggested.

Investigation of deep levels in semi-insulating GaAs by means of the temperature change piezoelectric photo-thermal measurements

“…This is a phenomenon in which all the optical and electrical activities of EL2 are extinguished when a GaAs sample is illuminated by a light at a wavelength about 1 m below 130 K. 2,3,6 The photoquenched state is said to be metastable because the optical and electrical activities can recover upon annealing the sample at around 150 K for a few minutes. This is a phenomenon in which all the optical and electrical activities of EL2 are extinguished when a GaAs sample is illuminated by a light at a wavelength about 1 m below 130 K. 2,3,6 The photoquenched state is said to be metastable because the optical and electrical activities can recover upon annealing the sample at around 150 K for a few minutes.…”

Piezoelectric Photo thermal and Surface Photo voltage Spectra of Chalcopyrite CuGaSe/sub 2/ Epitaxial Layers fabricated on semi-insulating GaAs

“…4 And peak X at 1.87eV was conjectured to be a band transition related to EL2 in GaAs. 5 The signal around 1.45eV is due to the band gap of GaAs substrate. Although the peak A remained constant, B-and C-band drastically decreased by the photo quenching.…”

Investigation of Carrier Recombination Processes in GaAs/AlAs Multiple Quantum Wells Using Piezoelectric Photothermal and Surface Photovoltage Techniques

“…Details of this method have been reported elsewhere. [9][10][11][12] A disk-shaped piezoelectric transducer (PZT; NEC TOKIN N-21) was directly attached to the rear surface of the sample using conducting paste to detect the elastic wave generated by the nonradiative recombination of photoexcited carriers. The sample was mounted on the cold finger of a liquid-nitrogen cryostat and a vacuum of approximately 1 Â 10 À3 Pa was induced.…”