ULTRAHIGH PURITY LIQUID-PHASE EPITAXIAL-GROWTH OF GAAS

Ultrahigh purity GaAs reproducibly grown by liquid phase epitaxy is reported. The attained purities, as represented by 77-K electron concentration as low as 4.1 x 10(12) cm-3 and mobility as high as 287000 cm2/Vs for n-type, and hole concentration as low as 2.6 x 10(12) cm-3 and hole mobility as high as 21200 cm2/Vs for p-type, are the highest reported so far. These high mobilities appear to be attainable only by conventional solution baking in hydrogen with a wide O2 concentration range of 0.007-1.34 ppm at 800-degrees-C for a time proportional to W4/3, where W is Ga quantity. Whether we get the UHP p- or n-type depends on a critical term which is peculiar to the Ga quality. Secondary ion mass spectrography trace profile analyses show that the impurities effectively eliminated during the solution baking are S, Si and even C.