Optical pumping and photoluminescence detection of spin-polarized electrons in uniaxially stressed gallium arsenide [Thesis]

Technical Report · Mon Mar 01 00:00:00 EST 1982

DOI:https://doi.org/10.2172/5263877· OSTI ID:5263877

Zorabedian, Paul ^[1]

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1. SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)

This work describes the development and application of an optical pumping and photoluminescence experiment for electron spin polarization measurements on semiconductor photocathode materials. We discuss the spin polarization increase that is produced by applying a uniaxial compression to a gallium arsenide crystal and selectively optically pumping the transition between the upper strain-split valence band and the conduction band. The electron spin polarization is measured by analysing the circular polarization of the photoluminescence. The relation between luminescence and spin polarizations is given by P_σ = P_hP_s $$\frac{τ_{s}}{τ_{s}+τ_{r}}$$ where P_σ is the luminescence circular polarization P_s is the spin polarization, and P_h is the hole coupling factor. For band edge excitation P_h is identical to P_s. In this expression, τ_s and τ_r are the spin relaxation and luminescence recombination times, respectively. From our data we infer an increase in P_s from 50% at zero stress to 70% for an applied [001] stress of 4.0 x 10⁹ dyn cm^-2 in a 1 x 10¹⁸ p-type GaAs crystal at T = 100^oK. For comparison, the maximum theoretical polarization at infinite stress is 80%. Our results show that the observed increase in polarization can be fit to a model function of the ratio δ_s/E_k where δ_s is the strain splitting energy and E_k of 0.017 eV agrees reasonably well with the calculated value of V_rms, the rms potential energy fluctuation of the band edge due to the ionized impurity potentials. From the known dependence of V_rms on doping and temperature, device operating curves are proposed which predict the relation between spin polarization and applied stress for various values or impurity concentration p and temperature T. The tunable infrared dye laser that was built to optically pump the gallium arsenide samples is compatible with the pulsed operation of the gallium arsenide spin-polarized electron source at SLAC. We give tuning curves and discuss the operating characteristics of this laser.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC03-76SF00515
• OSTI ID: 5263877
• Report Number(s): SLAC-248; SLAC-R-248; ON: DE82012425
• Resource Relation: Other Information: Portions of document are illegible
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
GALLIUM ARSENIDES
ELECTRON SPIN RESONANCE
COMPRESSION
DYE LASERS
ENERGY GAP
OPTICAL PUMPING
P-TYPE CONDUCTORS
PHOTOCATHODES
PHOTOLUMINESCENCE
RECOMBINATION
ARSENIC COMPOUNDS
ARSENIDES
CATHODES
ELECTRODES
GALLIUM COMPOUNDS
LASERS
LIQUID LASERS
LUMINESCENCE
MAGNETIC RESONANCE
MATERIALS
PNICTIDES
PUMPING
RESONANCE
SEMICONDUCTOR MATERIALS
360603* - Materials- Properties