165 research outputs found
Minority Hole Mobility in n+ GaAs
The minority hole diffusivity, or equivalently the hole mobility, was measured in n+GaAs with the zeroâfield timeâofâflight technique. The minority hole mobility was measured for the donor doping range of 1.3Ă1017 cmâ3 to 1.8Ă1018 cmâ3 and was found to vary from 235 to 295 cm2/Vâs. At the lower doping level, the minority hole mobility is comparable to the corresponding majority hole mobility, but at 1.8Ă1018 cmâ3 the minority hole mobility was 30% higher than the majority carrier hole mobility. These results have important implications for the design of devices such as solar cells and pnpâheterojunction bipolar transistors
Microsecond Lifetimes and Low Interface Recombination Velocities in Moderately Doped n-GaAs Thin Films
We have observed lifetimes greater than 1 ps in moderately doped, thin film, n-GaAs/A1a,Gae,As double heterostructure membranes formed by etching away the substrate. We attribute these ultralong lifetimes to enhanced photon recycling caused by the removal of the substrate. Nonradiative recombination in the bulk and at the interfaces is very low; the upper limit of the interface recombination velocity is 25 cm/S.-Such long lifetimes in GaAs doped at N,= 1.3 X 10â cme3 suggest that thin-film solar cells offer a potential option for achieving very high efficiencies
Zero-Field Time-of-Flight Measurements of Electron Diffusion in P+-GaAs
Minority electron diffusivities in p+-GaAs-doped NA =~1.4Ă1018 and ~1019 cm-3 have been measured in zero-field conditions with an extension of the zero-field time-of-flight technique. Extension of the technique to make it applicable to heavily doped p+-GaAs is described and zero-field data are discussed. Unexpectedly, majority carrier drag effects are not evident in a comparison of this data with recently reported high-field data. Low zero-field mobility of electrons in p+-GaAs has important implications for high-speed devices such as heterojunction bipolar transistors
Recommended from our members
Evaluation of Four Imaging Techniques for the Electrical Characterization of Solar Cells
The imaging techniques enable the possibility of higher-level quality control and defect analysis of solar cell materials in in-line production processes
Recommended from our members
Recombination Lifetimes Using the RCPCD Technique: Comparison with Other Methods
The theory and operation of the resonance-coupled photoconductive decay (RCPCD) technique is described. Examples are presented of data measured on a wide variety of sample types. The RCPCD technique has been applied to a variety of wafer and thin-film materials. Using this technique, we can measure recombination lifetime over at least three decades of injection level. We can also measure relative values of minority-carrier mobility and diffusion length. By scanning the excitation wavelength, we can measure spectral response and photoconductive excitation spectra. Deep-level impurities have been detected by several variations of RCPCD
Imaging charge and spin diffusion of minority carriers in GaAs
Room temperature electronic diffusion is studied in 3 mum thick epitaxial p+
GaAs lift-off films using a novel circularly polarized photoluminescence
microscope. The method is equivalent to using a standard optical microscope and
provides a contactless means to measure charge (L) and spin (L_s) diffusion
lengths. The measured values of L and L_s are in excellent agreement with the
spatially averaged polarization and a sharp reduction in these two quantities
(L from 21.3 mum to 1.2 mum and L_s from 1.3 mum to 0.8 mum) is measured with
increasing surface recombination. Outwards diffusion results in a factor of 10
increase in the polarization at the excitation spot.Comment: 13 pages, 3 figure
Recommended from our members
Modeling Minority-Carrier Lifetime Techniques that Use Transient Excess-Carrier Decay (Poster)
A study of minority carrier lifetime versus doping concentration in nâtype GaAs grown by metalorganic chemical vapor deposition
Timeâresolved photoluminescence decay measurements are used to explore minority carrier recombination in nâtype GaAs grown by metalorganic chemical vapor deposition, and doped with selenium to produce electron concentrations from 1.3Ă1017 cmâ3 to 3.8Ă1018 cmâ3. For electron densities n0\u3c1018 cmâ3, the lifetime is found to be controlled by radiative recombination and photon recycling with no evidence of ShockleyâReadâHall recombination. For higher electron densities, samples show evidence of ShockleyâReadâHall recombination as reflected in the intensity dependence of the photoluminescence decay. Still, we find that radiative recombination and photon recycling are important for all electron concentrations studied, and no evidence for Auger recombination was observed
Comparative study of minority electron properties in p+-GaAs doped with beryllium and carbon
Minority electron properties in p+âGaAs doped with beryllium (Be) and with carbon (C) are reported. Measurements of essentially identical responses for structures differing only in dopant element demonstrate that the diffusivity (Dn) and the diffusion lengths (Ln) are the same in p+âGaAs doped to âŒ1019 cmâ3 with Beâ and Câdopants. Zeroâfield timeâofâflight analysis yields Dn=35 cm2/s and internal quantum efficiency analysis yields Ln=2.4 ÎŒm, which implies a lifetime that is approximately at the estimated radiative limit. In addition, the majority Hall mobility was also found to be identical for the Beâ and Câdoped material
Recommended from our members
Modeling Minority-Carrier Lifetime Techniques That Use Transient Excess-Carrier Decay: Preprint
Lifetime spectroscopy is a valuable tool for the characterization of PV materials. This paper combines modeling and experimental results to illustrate the injection-level dependent response of three transient excess-carrier decay techniques
- âŠ