Arsenic precipitates have been observed in GaAs low-temperature buffer layers (LTBLs) used as "substrates" for normal molecular beam epitaxy growth. Transmission electron microscopy has shown the arsenic precipitates to be hexagonal phase single crystals. The precipitates are about 6±4 nm in diameter with a density on the order of 10 17 precipitates per cm). The semi-insulating properties of the LTBL can be explained in terms of these arsenic precipitates acting as "buried" Schottky barriers with overlapping spherical depletion regions. The implications of these results on LTBL resistivity stability with respect to doping and anneal temperature will be discussed as will the possible role of arsenic precipitates in semi-insulating liquid-encapsulated Czochralski-grown bulk GaAs. Recently, a new type of semi-insulating GaAs epilayer, known as a low-temperature buffer layer (LTBL) was found to reduce "sidegating" or "backgating", an important parasitic problem associated with GaAs field-effect transistor circuit technology.l Even though there is currently much interest concerning possible applications of this material, there is a certain "mystery" about its chemistry, atomic structure, and electronic properties. Most of this mystery is well documented by Kaminska et a1. 2 It can
Scanning tunneling microscopy is used to study low temperature grown (LTG) InGaAs with and without Be doping. The Be-doped material is observed to contain significantly fewer AsGa antisite defects than the undoped material, with no evidence found for Be–As complexes. Annealing of the LTG-InGaAs forms precipitates preferentially in the undoped material. The previously observed dependence of the optical response time on Be doping and annealing is attributed to changes in the As antisite concentration and the compensation effect of the Be.
We report on the transient photoconductivity of hot carriers in undoped bulklike In 0.53 Ga 0.47 As observed via time-resolved terahertz far-infrared spectroscopy. For very dilute photoexcitation densities of Ͻ1ϫ10 15 cm Ϫ3 and an initial excess carrier energy of 630 meV, we find that electrons have an effective intervalley L→⌫ return time of 3.1 ps as measured via the increased electrical conductivity associated with ⌫ electrons. In contrast, a total conductivity risetime of ϳ0.5 ps is observed for electrons with initial excess energy insufficient to cause intervalley scattering. The observed frequency dependent conductivity is analyzed via the Drude theory, allowing the determination of the temporal dynamics of the mobility at dilute excitation densities of ϳ1ϫ10 14 cm Ϫ3 .
A tunnel diode was formed from GaAs containing excess arsenic incorporated by molecular beam epitaxy at reduced substrate temperatures. The incorporation of excess arsenic during growth results in a more efficient incorporation of silicon on donor sites and beryllium on acceptor sites. The better dopant incorporation, along with trap assisted tunneling through deep levels associated with the excess arsenic, results in a tunnel junction with record peak current density of over 1800 A/cm2, zero-bias specific resistance of under 1×10−4 Ω cm, and a room-temperature peak-to-valley current ratio of 28.
Magnetotransport, magnetooptical, and electronic subband studies in In x Ga1−x As/In0.52Al0.48As oneside modulationdoped asymmetric step quantum wells Appl.Noncontact thickness and composition assessment of a strained AlGaAs/AlAs/InGaAs double barrier multiple quantum well structure
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