The structural, transport and optical properties of DA-pHEMT heterostructures are considered. Despite the high 2DEG density (~4×1012 cm-2), parallel conductance is almost lacking in DA-pHEMT heterostructures: the electron density in the parallel conducting layer does not exceed 11% of the 2DEG density, and the electron mobility is lower than the 2DEG mobility by a factor of more than 2.5. It was determined that the beryllium concentration in the undoped InGaAs QW does not exceed 2×016 cm-3 in spite of the Be segregation from the p+-doped barriers during the epitaxy growth. The results of the development of powerful DA-pHEMT are presented. Transistors with a gate length of 0.4-0.5 μm and a total gate width of 0.8 mm at a frequency of 10 GHz have a gain of more than 9 dB, an output power density of more than 1.6 W/mm, a power added efficiency up to 50%.