MOLECULAR-BEAM EPITAXY GROWTH AND PROPERTIES OF GAAS (ALGA)AS P-TYPE HETEROSTRUCTURES ON (100), (011), (111)B, (211)B, (311)B, AND (311)A ORIENTED GAAS/

We report on a series of Be-doped GaAs/AlGaAs two-dimensional hole gas (2DHG) structures grown on (110), (111)B, (211)B and (311)B oriented substrates and compare their properties with high-mobility samples gro wn on (311)A using Si doping. The samples were prepared and grown unde r the same conditions so as to render them comparable. They are found to have mobilities which are strongly anisotropic within the plane. Th e highest mobility is found on the (110) surface with similar to 100,0 00 cm(2) V-1 s(-1), while the (211)) surface gave the lowest values si milar to 10,000 cm(2) V-1 s(-1). However, the later samples are found to have quantum Hall effect critical currents of > 70 mu A: an excepti onally high value for a hole gas which makes them suitable for metrolo gy. All the samples show strong low-field positive magnetoresistance w ith resistance increases of up to 30% at magnetic fields of only 0.1 T . The presence of this feature on all the different planes shows that it does not depend upon the details of the band structure. It is ident ified with the lifting of the degeneracy of the spin sub-bands by the asymmetrical potential giving rise to a classical two-band magnetorere sistance.