Selective-area epitaxy (SAE) of carbon-doped (Al)GaAs by chemical beam epitaxy (CBE) using tris-dimethylaminoarsenic is investigated. Orientation of the growth front can significantly affect the growth rate of the regrown layers, resulting in facet formation around the mask. Moreover, the facets can be varied by adjusting the V/III ratio. For stripes along the [011̄] direction, the growth rate of (110) and (111)A planes is lowest when the V/III ratio is close to 1, resulting in lateral growth. This lateral growth has been exploited to fabricate heterojunction bipolar transistors (HBTs) with selectively regrown GaAs/AlGaAs:C external base layers. These HBTs exhibit a 62% reduction in the base sheet resistance and a higher current gain, compared to the original HBT strcuture. No degradation of the current gain is found after regrowth, demonstrating the great potential of SAE by CBE.
Planar separate-confinement, double-heterostructure, single-quantum-well photoelastic GaAs/AlGaAs lasers have been fabricated using a novel yet practical processing technique involving thin-film surface WNi stressors for waveguiding and ion implantation for isolation. A p++-GaAs contact layer regrown by chemical beam epitaxy has been used to improve the WNi ohmic contacts to the lasers. Even without bonding on heat sinks, these planar photoelastic lasers operate at continuous wave at room temperature. The lowest threshold is 29 mA for a cavity length of 178 μm and a stressor width of 5 μm. The internal quantum efficiency above threshold is 75%. The characteristic temperature is 114 K. The main waveguiding mechanism of the photoelastic lasers is determined to be weak index guiding with the beam waist in the junction plane measured 10 μm behind the end facet.
In this paper, we report laser-assisted chemical beam epitaxy (CBE) of GaAs using triethylgallium (TEGa), tris-dimethylaminoarsenic (TDMAAs), and an ar ion laser operating at visible or ultraviolet (UV) wavelength. the laser-assisted growth with TDMAAs, compared to as4 or asH3, shows a wider range of growth enhancement at low substrate temperatures. Unlike CBE of GaAs without laser irradiation, laser-enhanced GaAs growth rate was found to be constant as the V/III incorporation ratio changes. by using diiodomethane (CI2H2) as a dopant gas, the GaAs films with laser irradiation show a much higher hole concentration than those grown simultaneously without laser irradiation at substrate temperatures from 460-530°C. Laser irradiation was also found to enhance silicon incorporation at low temperatures. Photothermal effects are responsible for laser-enhanced growth and silicon doping, but the wider temperature window in laser-enhanced growth and the laser-enhanced carbon incorporation are caused by additional photocatalytic or photochemical effects.
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