Doping dependence and anisotropy of minority electron mobility in molecular beam epitaxy-grown p type GaInP

The article of record as published may be found at http://dx.doi.org/10.1063/1.4902316Direct imaging of minority electron transport via the spatially resolved recombination luminescence signature has been used to determine carrier diffusion lengths in GaInP as a function of doping. Minority electron mobility values are determined by performing time resolved photoluminescence measurements of carrier lifetime on the same samples. Values at 300 K vary from~2000 to 400 cm2/V s and decrease with increasing doping. Anisotropic diffusion lengths and strongly polarized photoluminescence are observed, resulting from lateral composition modulation along the [110] direction. We report anisotropic mobility values associated with carrier transport parallel and perpendicular to the modulation direction.USDOEAC05-06OR23100DEAC36-08GO28308This work was supported at the Naval Postgraduate School in part by National Science Foundation Grant No. DMR-0804527 and in part by the NPS Energy Academic Group with funding from the Navy Energy Coordination Office. T.C. acknowledges support from the Department of Energy, Office of Science Graduate Fellowship Program (DOE SCGF), made possible in part by the American Recovery and Reinvestment Act of 2009, administered by ORISE-ORAU under Control No. DE-AC05-06OR23100. TRPL work at NREL was supported by the Department of Energy Office of Science, Basic Energy Sciences under DEAC36-08GO28308

TRANSIENT AND TEMPERATURE-DEPENDENT PHENOMENA IN Ge:Be AND Ge:Zn FAR INFRARED PHOTOCONDUCTORS

An experimental study of the transient and temperature-dependent behavior of Ge:Be and Ge:Zn photoconductors has been performed under the low background photon flux conditions (p dot approx. = 10/sup 8/ photons/second) typical of astronomy and astrophysics applications. The responsivity of Ge:Be and Ge:Zn detectors is strongly temperature-dependent in closely compensated material, and the effect of compensation on free carrier lifetime in Ge:Be has been measured using the photo-Hall effect technique. Closely compensated material has been obtained by controlling the concentration of novel hydrogen-related shallow acceptor complexes, A(Be,H) and A(Zn,H), which exist in doped crystals grown under a H/sub 2/ atmosphere. A review of selection criteria for multilevel materials for optimum photoconductor performance is included. 55 refs., 47 figs

Imaging transport in nanowires using near-field detection of light

The article of record as published may be found at http://dx.doi.org/10.1016/j.jcrysgro.2011.12.067Major progress in the crystal growth of nanowires and related structures places new demands on our abilities to characterize optical and electronic properties with both an ease and a resolution commensurate with the materials of interest. In particular, transport properties, such as minority carrier diffusion length, are important for a range of applications in light emission, sensing and solar energy conversion. In this paper, a technique to "image transport" in nanostructures by monitoring the motion of charge via the recombination emission of light is reviewed. Transport imaging combines the resolution of near-field optics with the charge generation control of a scanning electron microscope. The technique is related to, but significantly different from standard cathodoluminescence, since it maintains the spatial information of the emitted light. Light is collected in the near-field from a scanning fiber in an atomic force microscope/near-field scanning optical microscope system. It is possible to determine minority carrier or exciton diffusion lengths from a single optical image, without any electrical contact to the sample. New results are presented for minority carrier hole transport in ZnO nanowires and nonobelts.National Science Foundation Grant DMR 0804527Nano-MEMS program of DARPANational Science FoundationNational Science Foundation Grant DMR 0804527Nano-MEMS program of DARP