GROWTH OF HIGH-QUALITY P-TYPE GAAS EPITAXIAL LAYERS USING CARBON TETRABROMIDE BY GAS-SOURCE MOLECULAR-BEAM EPITAXY AND MOLECULAR-BEAM EPITAXY

Heavily C-doped p-type GaAs epitaxial films have been grown using carbon tetrabromide (CBr4) as a dopant source in both gas source molecular-beam epitaxy (GSMBE) and molecular-beam epitaxy (MBE). It was found that CBr4 has a great potential as a p-type dopant source for use in a conventional MBE chamber without any major modification of its pumping system because of its high-doping efficiency and low gas load. Hole concentrations in excess of 1 X 10(20) CM-3 have been measured in CBr4-doped GaAs grown from both the MBE or GSMBE techniques, using AS4 Or AsH3, respectively. A Hall mobility of > 80 cm2/V s was measured in layers with doping level of 5 X 10(19) CM-3, which is comparable to that from chemical beam exitaxially (CBE) grown TMGa-doped GaAs. Under GSMBE and MBE modes, the doping memory effect in AlGaAs was greatly reduced using CBr4 as compared to TMGa doping source. GSMBE grown heterojunction bipolar transistors with a CBr4-doped base layer have a current gain as high as 79 and a base sheet resistance as low as 225 OMEGA/square.