Search

The deep trap energy (E(T)) and deep trap concentration (N(T)) in GaAs are determined by a new method, which does not require the emission-rate data. The method involves measurement of capacitance at different forward bias voltages. The concentration of the various deep trap centers such as EL6, EL3 and EL2 are determined by considering the lambda effect. N(EL2) has a value of 1.14 times 10 to the 16th power per cubic centimeter and E(EL2) has a value of 0.71 electron volts. N(EL6) has a value of 8 times 10 to the 15th power per cubic centimeter and E(EL6) has a value of 0.42 electron volts.

Deep-level transient spectroscopic studies of molecular-beam epitaxially-grown, Si-doped GaAs layers reveals an 0. 65 eV electron trap associated with As(Ga) lambda effects. The overlapping peaks are studied numerically. The electron trap is also related to the EB4 trap in electron irradiated GaAs layers.

The annealing dynamics of GaAs grown by molecular beam epitaxy at 200 degrees celsius on a 650 micrometer substrate were investigated using Hall effect and conductivity measurements. The results showed that at 300K, the hopping conduction was significantly stronger than band conduction regardless of annealing temperature. The dominant acceptor initially decreased but later increased as the annealing temperature increased.

The mechanisms for GaAs surface passivation by a molecular beam epitaxial cap layer grown at 200 degrees centigrade were investigated. The results showed that a thin undoped molecular beam epitaxial cap layer greatly limited the free-electron depletion. Normal surface states were not present and a dense donor and high donor interface charge were observed.

Hole scattering occurs from the alloy potential of alloys such as aluminum gallium arsenate. Although alloy scattering is weak for carriers possesing small effective masses, it can be strong for heavy carriers. Alloy scattering must then be considered when calculating hole mobilities in aluminum gallium arsenates. A study on alloy scattering in p-type aluminum gallium arsenates presented an accurate calculation of hole-mobility with x ranging from 0 to 1. Alloy scattering was found to reduce hole mobility almost a factor of 2 while the alloy potential was estimated at about .5 electron volts.

The dominant electrically active defect produced by 0.42 MeV electron irradiation in GaN is a 70 meV donor. Since only N-sublattice displacements can be produced at this energy, and since theory predicts that the N interstitial is a deep acceptor in n-type GaN, we argue that the 70 meV donor is most likely the isolated N vacancy. The background shallow donors, in the 24–26 meV range, actually decrease in concentration, probably due to interactions with mobile N interstitials that are produced by the irradiation. Thus, the recent assignment of a photoluminescence (PL) line as an exciton bound to a 25 meV N-vacancy donor is incompatible with our results. Moreover, we do not observe that PL line in our sample. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents the Hall effect measurements on gallium arsenide semiconductors grown at low temperatures by molecular beam epitaxy. Analysis on the capped, conductive layers of the structure; Determination of the donor and acceptor concentration and activation energy in the materials.