(Color online) Comparison of partial pressures of mass 18 (H2O), 28 (N2/CO), 44 (CO2), 75 (As), and 91 (AsO) in the growth chamber when the shroud is cooled with LN2 (left columns) and to −70 °C with the silicone coolant (right columns). The top of each color bar indicates the partial pressure for the system in the configuration corresponding to that color. In the case of mass 28, there is no bar for the room temperature shroud and TSP configuration as the pressure was the same when the shroud was at room temperature and at −70 °C.
(Color online) Residual gas mass spectra with (a) the system configured for LN2 and (b) the system configured for the Syltherm coolant with LN2 in the sublimation pump trap. Cooling the system results in similar reductions of gas partial pressures for both cooling configurations. The cells were in idle mode (200–400 °C) and the substrate heater was off.
(Color online) Room temperature photoluminescence intensity for n- and p-type GaAs samples grown under the same growth conditions with LN2 and the closed cycle chiller.
(Color online) DLTS spectra for (a) p-type samples (emission rate is 116.2 s−1) and (b) n-type samples (emission rate is 23.3 s−1) grown with the shroud cooled with LN2 and the closed cycle chiller. Steady reverse bias voltages of 1.0 and 2.0 V were used for p-GaAs samples grown with LN2 and the chiller setup, respectively, with a filling voltage of 0.5 V for 2 ms. For both n-type samples, the reverse voltage was 2.0 V and the filling voltage was 0 V for 2 ms.
Concentrations of all deep levels seen in p-GaAs and n-GaAs samples grown with the shroud cooled with LN2 and the closed cycle chiller at −70 °C as determined by DLTS.
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