Tetsuo Ikari

Optical and electrical properties of layer semiconductor p‐GaSe doped with Zn

Zinc (Zn) is doped into GaSe single crystals grown by the Bridgman technique in a wide range from 0.005 to 0.5 at. % to the stoichiometric melt. Radiative recombination mechanisms have been investigated by using photoluminescence (PL) measurements. The PL spectra in Zn‐doped samples at 77 K are dominated by three emission bands at 1.75, 1.63, and 1.27 eV. The 1.63 and 1.27 eV emission bands are enhanced with the increase in the amount of Zn. In addition to the results of Hall effect measurements, it is found that the 1.63 and 1.27 eV emission bands are associated with the acceptor levels at 0.12 and 0.3 eV above the valence band, respectively. For the 1.27 eV emission band, the temperature dependences of the PL intensity, peak energy, and half‐width are characterized by the configurational coordinate model.

Theoretical and experimental aspects of three-dimensional infrared photothermal radiometry of semiconductors

A general theoretical model for the infrared photothermal radiometric (PTR) signal from a semiconductor wafer is developed for the case of three-dimensional sample geometry with finite thickness. Carrier diffusion and heat conduction along the radial direction of the sample as well as along the thickness coordinate are taken into account. The simulated results for the modulation frequency dependence of the PTR signal amplitude and phase are applied to experimental data from Si wafers. Good agreement between the theoretical and experimental curves is obtained and several electronic and thermophysical parameters are estimated. This indicates that the three-dimensional PTR measurement is useful to remotely characterize semiconductor wafers patterned for large scale integrated circuits.

Electrical properties of vapour grown tellurium single crystals

Abstract Resistivity measurements of vapour grown tellurium single crystals are carried out from room to liquid helium temperature. The crystal shows a metallic behavior above 40 K and the observed T 2 dependence of the resistivity is explained by assuming that the carriers flow along the chain and the interchain interaction is sufficiently weak. The log T behavior of the resistivity below 40 K suggests that the carriers are scattered by the magnetic centers.

Photoluminescence spectra of p-GaSe doped with Cd

Impurity levels in Cd‐doped GaSe have been studied by using photoluminescence (PL) measurements. The PL spectra at 77 K are dominated by three new emission bands at 1.95, 1.75, and 1.62 eV. The PL intensity and the peak energy of the 1.95 and 1.62 eV emission bands are measured as a function of the temperature. It is shown that the 1.95 eV emission band is due to the transition between the conduction band and the acceptor level at 0.18 eV above the valence band. The 1.62 eV emission band is caused by the transition from the donor level at 0.37 eV below the conduction band to the acceptor level at 0.13 eV above the valence band. The PL intensity increases with increasing Cd concentration.

Impurity levels in layer semiconductor p‐GaSe doped with Mn

The impurity levels in Mn‐doped GaSe have been investigated by using photoluminescence (PL), Hall effect (HE), and deep‐level transient spectroscopy (DLTS) measurements. The emission band at 1.82 eV is observed on the PL spectra of the samples doped with Mn of wide range from 0.01 to 1.0 at. %. We find, from the temperature dependences of PL intensity and peak energy, that the 1.82 eV emission band is due to the transition between the conduction band and the acceptor level at 0.32 eV above the valence band. The acceptor level located at about 0.34 eV above the valence band is detected by using HE and DLTS measurements. The dominant acceptor level in the carrier transport shows almost the same position as that of the radiative recombination center. This acceptor level is probably associated with the defects formed by Mn atoms in the interlayer or interstices.

Piezoelectric detection of the photoacoustic signals of n‐type GaAs single crystals

Piezoelectric photoacoustic (PA) measurements on liquid‐encapsulated‐Czochralski‐grown n‐GaAs were carried out at room temperature. A continuous broad band below 1.35 eV and a peak at 1.383 eV were observed in the PA amplitude spectra. By comparing with the optical‐absorption spectra, it is concluded that the broad band is due to the electron transition involving the EL2 deep‐lying defect levels. For the observed peak at 1.383 eV, the origin is considered to be dislocation related. The possibility that this peak is an apparent one expected from the proposed models for the PA signal generation is denied.

Zn‐induced impurity levels in layer semiconductor InSe

The impurity levels in Zn‐doped InSe have been investigated by photoluminescence (PL), Hall effect (HE), and deep‐level transient spectroscopy (DLTS). Previous analysis by PL spectra shows that the radiative transition is dominated by donor‐Zn acceptor pairs. In the present work, a search was made for the deep acceptor level using the combined data from HE and DLTS measurements. We find that the deep acceptor level, which is associated with defects or defect complexes formed by Zn atoms in the interlayer, is located about 0.6 eV above the valence band.

Temperature dependence of photoluminescence of layer semiconductor p-GaTe

The photoluminescence (PL) spectra of undoped p-GaTe at 97 K are dominated by two emission bands at 1.76 and 1.59 eV. For the 1.76 eV emission band, the behavior of the peak energy and full-width at half-maximum as a function of temperature shows the characteristics of the recombination mechanism for the free exciton. We find, from the temperature dependence of the PL intensity of the 1.59 eV emission band, that the band is caused by the transition from the donor level to the acceptor level located at 0.15 eV above the valence band.

Electrical properties of layer semiconductor p‐GaSe doped with Cu

Measurements of Hall effect and deep‐level transient spectroscopy have been made on Cu‐doped p‐GaSe. The moderately deep acceptor and shallow acceptor levels located at 0.13 and 0.04 eV above the valence band are obtained from the temperature dependence of the hole concentration. The hole‐trapping level at 0.14 eV above the valence band is detected by deep‐level transient spectroscopy and shows almost the same position as the moderately deep acceptor level. We find that the shallow acceptor level of 0.04 eV is attributed to Cu atoms, whereas the moderately deep acceptor level of 0.13 eV is governed by the defects or defect complexes.

Electrical characteristics of layer semiconductor p‐GaSe doped with Cd

The electrical properties of Cd‐doped GaSe have been investigated by using Hall‐effect and deep‐level transient spectroscopy (DLTS). The temperature dependence of hole concentration shows the characteristic of a partially compensated p‐type semiconductor. The moderately deep acceptor level at about 0.28 eV above the valence band is detected by using both Hall‐effect and DLTS measurements. We find that the acceptor level is associated with Cd‐related defects formed by the dopant atoms.