Very high quality p-type AlxGa1-xN/GaN superlattice has been achieved through optimization of Mg flow and period of superlattice. Theoretical model was used to optimize the structure of superlattice by choosing suitable Al compositions and superlattice periods. The experiments show that for x = 0.26, the resistivity is as low as 0.19 Omega cm and hole concentration is as high as 4.2 x 10(18) cm(-3), the highest values ever reported for p-type AlGaN/GaN superlattices. Hall effect measurement and admittance spectroscopy on the samples confirm the high quality of the superlattices. The activation energy calculated for p-type GaN and p-type A(0.1)Ga(0.9)N/GaN superlattice is estimated to be similar to125 and 3 meV respectively. (C) 2002 Elsevier Science Ltd. All rights reserved.