DLTS measurements have been performed on InGaAsN. Four hole traps have been identified in 1.05eV, p-type InGaAsN and the removal of a midgap trap (∼0.5eV) during annealing has been correlated with improved bulk material properties. Improvements in MOCVD growth conditions resulted in a reduction of trap density in 1.05eV, p-type InGaAsN. Increased indium and nitrogen composition has been correlated with higher defect concentrations in p-type InGaAsN. Two electron traps have been identified in 1.15eV, n-type InGaAsN and annealing was found to reduce the density of the shallow electron trap.

The deep level spectra in both p+-n homojunction and n-type Schottky GaN diodes are studied by deep level transient spectroscopy (DLTS) in order to compare the role of the junction configuration on the defects found within the n-GaN layer. Both majority and minority carrier DLTS measurements are performed on the diodes allowing the observation of both electron and hole traps in n-GaN. An electron level at Ec−Et=0.58 and 0.62 V is observed in the p+-n and Schottky diodes, respectively, with a concentration of ∼3−4×1014 cm−3 and a capture cross section of ∼1−5×10−15 cm2. The similar Arrhenius behavior indicates that both emissions are related to the same defect. The shift in activation energy is correlated to the electric field enhanced-emission in the p+-n diode, where the junction barrier is much larger. The p+-n diode configuration allows the observation of a hole trap at Et−Ev=0.87 eV in the n-GaN which is very likely related to the yellow luminescence band.

N-Schottky and p+–n GaN junctions are currently used for different technologies. A comparison of the deep levels found throughout the entire band gap of n-GaN grown by metal-organic chemical vapor deposition under both configurations is presented. Both deep level optical spectroscopy and deep level transient spectroscopy measurements are used allowing the observation of both majority and minority carrier traps. Deep levels at Ec−Et=0.58–0.62, 1.35, 2.57–2.64, and 3.22 eV are observed for both diode configurations, with concentrations in the ∼1014–1016 cm−3 range. The 0.58–0.62 eV level appears correlated with residual Mg impurities in the n side of the p+–n diode measured by secondary-ion-mass spectroscopy, while the 1.35 eV level concentration increases by a factor of ∼4 for the Schottky junction possibly correlating with the carbon profile. The 2.57–2.64 eV level is a minority carrier hole trap in n-GaN, likely related to the yellow photoluminescence band, and is detected both optically from the conduction band (2.64 eV) and thermally from the valence band (0.87 eV).

The influence of initial growth conditions and lattice matching on the deep level spectrum of n-ZnSe grown on GaAs by molecular-beam epitaxy is investigated by means of deep level optical spectroscopy. A detailed study of both the steady-state and transient photocapacitance allows us to measure optical threshold energies, concentrations, and emission rates of electronically active defects in the ZnSe layer. Several deep levels are found in the ZnSe layer at Ec−Et=1.15, 1.46, 1.90, and 2.25 eV with concentrations in the 1012–1014 cm−3 range. When a 2-nm-thick composition controlled interface layer is grown at different beam pressure ratios prior to the ZnSe growth, a distinct decrease in the 1.46 eV level concentration with increasing Se content is found. Deposition of a lattice-matched InxGa1−xAs buffer layer prior to the ZnSe growth reduces the concentration of both the 1.15 and 1.46 eV levels by over an order of magnitude, indicating the role of lattice matching in the ZnSe overlayer. We also perform depth profiling of the defect distributions within the ZnSe overlayer to see the effect of the ZnSe thickness on the concentration of these levels as well as their possible association to the ZnSe/GaAs interface. We find that only the 2.25 eV level concentration shows a dependence on depth, increasing as the II–VI/III–V interface is approached.

A midgap deep level in n-type ZnSe grown by molecular beam epitaxy (MBE) on In0.04Ga0.96As/GaAs is detected and investigated by deep level optical spectroscopy and cathodoluminescence spectroscopy. The deep level has an optical threshold energy of 1.46 eV below the conduction band edge, and its concentration strongly depends on the Zn:Se beam pressure ratio during initial nucleation of the ZnSe layer. The concentration of this level decreases by a factor of ∼8 for Se rich vs Zn rich nucleation conditions, correlating with a decrease in the Se vacancy concentration for Se-rich nucleation. The investigation of photocapacitance transients revealed a strong interaction of the 1.46 eV level with both the conduction and the valence bands. Moreover, this level showed the largest optical cross section (emission rate of ∼103 s−1) of all of the levels found in the ZnSe layer. Taken together, these observations suggest this level may be an important recombination-generation center in MBE-grown ZnSe devices on GaAs substrates.

Deep-level transient spectroscopy measurements were utilized to investigate deep-level defects in metal–organic chemical vapor deposition-grown, unintentionally doped p-type InGaAsN films lattice matched to GaAs. The as-grown material displayed a high concentration of deep levels distributed within the band gap, with a dominant hole trap at Ev+0.10 eV. Postgrowth annealing simplified the deep-level spectra, enabling the identification of three distinct hole traps at 0.10, 0.23, and 0.48 eV above the valence-band edge, with concentrations of 3.5×1014, 3.8×1014, and 8.2×1014 cm−3, respectively. A direct comparison between the as-grown and annealed spectra revealed the presence of an additional midgap hole trap, with a concentration of 4×1014 cm−3 in the as-grown material. The concentration of this trap is sharply reduced by annealing, which correlates with improved material quality and minority-carrier properties after annealing. Of the four hole traps detected, only the 0.48 eV level is not influenced by annealing, suggesting this level may be important for processed InGaAsN devices in the future.

Deep level defects have been detected and analyzed in epitaxial ZnSe layers grown by molecular beam epitaxy (MBE) on GaAs and on In0.04Ga0.96As using deep level optical spectroscopy (DLOS). A series of samples, which differ only in the initial Zn:Se beam pressure ratio (BPR = 1:1, 1:10, 10:1) during the growth nucleation step, were characterized by DLOS in order to assess the dependence of bulk deep level formation on interface nucleation conditions. The transient and steady state photocapacitance measurements were performed using 100 W Quartz Halogen and 450 W Xe lamps as light sources, in the spectral range of 0.9 to 2.9 eV with a resolution better than 0.02 eV. The capacitance transients were recorded for time windows of 10 msec to 5 sec after light excitation of the sample, which was kept at a temperature of 100 K. Using semi-transparent Au Schottky contacts, several deep levels in the ZnSe layer were detected for all BPR’s, with optical threshold energies of 1.1, 1.46 and 1.9 eV below the conduction band. These energies were obtained from the slope of the capacitance transient at different time intervals and were confirmed by steady state photocapacitance. The concentration of the levels was in the range 1012 to 1014 cm−3. Both the 1.1 and 1.46 eV trap concentrations were found to depend strongly on lattice mismatch conditions, whereas the latter was shown to largely depend on BPR. The optical threshold of the 1.9 eV trap correlates well with a ≈1.9 eV cathodoluminescence (CL) peak, which has been previously associated with either Zn vacancies or Gazn substitutional defects in Zn-deficient material.