A5088144816- Advanced Semiconductor Detectors and Materials
- Chalcogenide Semiconductor Thin Films
- Quantum Dots Synthesis And Properties
- Electronic and Structural Properties of Oxides
- Advanced Materials Characterization Techniques
- Semiconductor Quantum Structures and Devices
Texas State University
2014-2018
National Renewable Energy Laboratory
2014
Double heterostructures (DH) were produced consisting of a CdTe film between two wide band gap barriers CdMgTe alloy. A combined method was developed to quantify radiative and non-radiative recombination rates by examining the dependence photoluminescence (PL) on both excitation intensity time. The measured PL characteristics, interface state density extracted modeling, indicate that efficiency CdMgTe/CdTe DHs is comparable AlGaAs/GaAs DHs, with densities in low 1010 cm−2 carrier lifetimes...
Heterostructures with CdTe and CdTe1-xSex (x ∼ 0.01) absorbers between two wider-band-gap Cd1-xMgxTe barriers 0.25–0.3) were grown by molecular beam epitaxy to study carrier generation recombination in bulk materials passivated interfaces. Using a combination of confocal photoluminescence (PL), time-resolved PL, low-temperature PL emission spectroscopy, extended defect types identified the impact these defects on charge-carrier was analyzed. The dominant dislocations samples (211)B...
CdSeTe/CdMgTe double heterostructures were produced with both n-type and unintentionally doped absorber layers. Measurements of the dependence photoluminescence intensity on excitation carried out, as well measurements time-resolved decay after an pulse. It was found that times under very low photon injection conditions are dominated by a non-radiative Shockley-Read-Hall process described using recombination center asymmetric capture cross section, where section for holes is larger than...
Time-resolved and time integrated photoluminescence (PL) studies are reported for undoped doped CdMgTe/CdSeTe double heterostructures (DHs) grown by molecular beam epitaxy. Undoped DHs studied with absorber layer thickness varying from 0.5 to 2.5 µm. The n-type free-carrier concentration is varied ~7 × 1015, 8.4 1016, 1017 cm−3 using iodine as a dopant in different thicknesses (0.25–2.0 µm). Optical injection 1 1010 3 1011 photons/pulse/cm2, corresponding the initial of photo-carriers up ~8...
Recent studies have demonstrated that growth of CdTe on (100) and (211)B substrates via molecular beam epitaxy (MBE) results in planar defect densities 2 3 orders magnitude higher than InSb substrates, respectively. To understand this shortcoming, MBE with a variety substrate preparation methods is studied by scanning electron microscopy, secondary ion mass spectrometry, x-ray photoelectron spectroscopy, cross sectional transmission atom probe tomography (APT). Prior to growth, carbon shown...
Low-temperature photoluminescence (LTPL) and time-resolved (TRPL) were used to study bulk material interface properties of MBE-grown CdTe. CdTe ternary-alloy double heterostructures (DH) grown on InSb substrates show LTPL emission from excitons, dislocations, other defects. Photoluminescence spectra changed with composition quality, near-band exciton emissions increasing related extended point defects decreasing as defect density decreased interfaces improved. Measured lifetimes TRPL decay...
Intensity-resolved and time-resolved PL are shown to be powerful tools for analyzing recombination in epitaxial CdTe appropriate photovoltaic applications. Non-radiative defects such as dislocations easily mapped quantified by confocal photoluminescence. Very low dislocation density twin content, well very high luminescence efficiency measured lifetime (450 ns), can achieved Se-alloying lattice match CdTeSe InSb substrates. Analysis suggests the bulk is excess of 700 ns.