Influence of deep levels on the electrical transport properties of CdZnTeSe detectors

We investigated the influence of deep levels on the electrical transport properties of CdZnTeSe radiation detectors by comparing experimental data with numerical simulations based on simultaneous solution of drift-diffusion and Posisson equations, including the Shockley-Read-Hall model of the carrier trapping. We determined the Schottky barrier height and the Fermi level position from I-V measurements. We measured the time evolution of the electric field and the electrical current after application of a voltage bias. We observed that the electrical properties of CZTS are fundamentally governed by two deep levels close to the mid-bandgap - one recombination and one hole trap. We show that the hole trap indirectly increases the mobility-lifetime product of electrons. We conclude that the structure of deep levels in CZTS are favorable for high electrical charge transport.Comment: 11 pages, 6 figures, 1 tabl

Iron-induced deep-level acceptor center in GaN/AlGaN high electron mobility transistors:Energy level and cross section

Dynamic transconductance dispersion measurements coupled with device physics simulations were used to study the deep level acceptor center in iron-doped AlGaN/GaN high electron mobility transistors (HEMT). From the extracted frequency dependent trap-conductance, an energy level 0.7 eV below the conduction band and a capture cross section of 10(-13) cm(2) were obtained. The approach presented in this work avoids the non-equilibrium electrical or optical techniques that have been used to date and extracts the device relevant trap characteristics in short channel AlGaN/GaN HEMTs. Quantitative prediction of the trap induced transconductance dispersion in HEMTs is demonstrated

Defects in Cu2O studied by deep level transient spectroscopy

Hole traps in p-type Cu2O were studied by means of deep level transient spectroscopy in the heterostructure of p-Cu2O/i-ZnO/n-ZnO. In addition to the trap level at about 0.45 eV from the valance band edge, which is already reported as being due to Cu vacancy, we found a new trap level at about 0.25 eV. The new trap is tentatively assigned as Cu-di-vacancy from the trap concentration dependence on oxygen flow rate and substrate temperature

Fast C-V method to mitigate effects of deep levels in CIGS doping profiles

In this work, methods to determine more accurate doping profiles in semiconductors is explored where trap-induced artifacts such as hysteresis and doping artifacts are observed. Specifically in CIGS, it is shown that this fast capacitance-voltage (C-V) approach presented here allows for accurate doping profile measurement even at room temperature, which is typically not possible due to the large ratio of trap concentration to doping. Using deep level transient spectroscopy (DLTS) measurement, the deep trap responsible for the abnormal C-V measurement above 200 K is identified. Importantly, this fast C-V can be used for fast evaluation on the production line to monitor the true doping concentration, and even estimate the trap concentration. Additionally, the influence of high conductance on the apparent doping profile at different temperature is investigated

Platinum diffusion into silicon from PtSi

We have observed platinum diffusion into the silicon underlying a PtSi film. Silicon substrates covered with platinum films were annealed at temperatures from 300 to 800°C to form the silicide. Backscattering spectrometry spectra show no degradation of the silicide in the samples treated below 700°C. Deep level transient spectroscopy (DLTS) was used to measure diffused platinum electron traps. Electron trap concentrations in samples treated below 700°C are below the DLTS detection limit of 5×10^11/cm^3. Trap concentration profiles for the samples annealed at higher temperatures were obtained. These profiles cannot in general be explained by simple diffusion from an infinite source of platinum at the surface

Trapping-detrapping fluctuations in organic space-charge layers

A trapping-detrapping model is proposed for explaining the current fluctuation behavior in organic semiconductors (polyacenes) operating under current-injection conditions. The fraction of ionized traps obtained from the current-voltage characteristics, is related to the relative current noise spectral density at the trap-filling transition. The agreement between theory and experiments validates the model and provides an estimate of the concentration and energy level of deep traps

High-temperature deep-level transient spectroscopy system for defect studies in wide-bandgap semiconductors

Full investigation of deep defect states and impurities in wide-bandgap materials by employing commercial transient capacitance spectroscopy is a challenge, demanding very high temperatures. Therefore, a high-temperature deep-level transient spectroscopy (HT-DLTS) system was developed for measurements up to 1100 K. The upper limit of the temperature range allows for the study of deep defects and trap centers in the bandgap, deeper than previously reported by DLTS characterization in any material. Performance of the system was tested by conducting measurements on the well-known intrinsic defects in n-type 4H-SiC in the temperature range 300-950 K. Experimental observations performed on 4H-SiC Schottky diodes were in good agreement with the literatures. However, the DLTS measurements were restricted by the operation and quality of the electrodes