The un doped GaAs epitaxtial layer the thickness of which is about 1 μm has been growmn by the MOCVD system. The morphology was not good. And $n=10^{16}cm^{-3}$, $\mu H_n=2000cm^2/Vs$ was obtained at V/III =25, $T_s=650C$. Which I think the epitaxial layer is thin so the depletion layer has been developed and the impurities in the semi-insulating substrate has been diffused into the epitaxial layer by the high growth temperature. But, the good 20 K PL measurement of FWHM 4meV was obtained. And as the V/III ratio increases the carbon contamination conspicuously decreases. The growth rate at the mid-temperature range(600-675 C) is dependent linearly and only on the TMG mole fraction($X_{TMG}$) if the total flow rate ($Q_T$) is constant. And 410 A/min at $X_{TMG}=1\times10^{-4}$ and $Q_T =21/min$ (the linear gas velocity of 10 cm/s) was obtained.
