Temperature-dependent photoluminescence measurements were carried out between 8 and 300 K on CuInS 2 single crystals grown by a traveling heater method. Ten distinct peaks were present in the near-band edge region. Four unknown peaks, observed at 8 K, were found to be due to bound exciton emission. Moreover, the luminescence remained stable up to room temperature.

Undoped and Ga-doped (3 wt %) n-type ZnO thin films were grown by a reactive plasma deposition method on glass substrates at 200 °C under an oxygen flow rate from 0 to 50 SCCM. In this paper, we report on the defect and band edge related signals in the optical absorption spectra for ZnO thin film by using a piezoelectric photothermal (PPT) spectroscopy, which is effective in observing a nonradiative transition process. The PPT peak around 2.5 eV was observed only for the undoped ZnO samples grown under a low oxygen flow rate. This signal is considered to be related to the oxygen vacancies, because it disappears with the increase of the oxygen flow rates. No corresponding peak was found for the Ga-doped samples. This result indicates that Ga doping inhibits the generation of the oxygen vacancies, and it agrees with that from the first-principle electronic band structure calculations. We have also carried out the theoretical calculation for the optical absorption edge of degenerated ZnO as a function of the carrier concentration. Burstein-Moss effect and band-gap-narrowing effect in ZnO should be considered in the case of high carrier concentration. Comparing the experimental results with the theoretical predictions, we found out that the proposed PPT edge energy coincides well with the Fermi level EF.

Articles you may be interested inCarrier-density-wave transport property depth profilometry using spectroscopic photothermal radiometry of silicon wafers I: Theoretical aspects J. Appl. Phys. 93, 5236 (2003); 10.1063/1.1565498Carrier-density-wave transport property depth profilometry using spectroscopic photothermal radiometry of silicon wafers II: Experimental and computational aspects

Thin films of guest-free type-II Si clathrate (Si136) were fabricated on Si(111) wafers in two steps: NaxSi136 thin-film formation by thermal decomposition of NaSi precursor films and Na removal from the NaxSi136 film by a heat treatment with iodine. Cross-sectional TEM observation and XRD and Raman measurements verified the formation of 1-µm-thick Si136 films on the Si wafer. Since the prepared films showed n-type conduction, pn junction devices were developed by a Si136/p-type Si structure. This device showed a photovoltaic (PV) response under white light illumination. The thin film formation and the PV response of Si136 indicated this Si allotrope to be the next-generation platform for semiconductor technology.

The deep levels in GaTe single crystal have been investigated by deep-level transient spectroscopy measurements. The hole-trapping level is detected at 0.8 eV above the valence band. It is found that the deep level is associated with the defect or defect complex and the concentration increases with increasing annealing temperature.