Investigation of delta-doped pHEMT InGaAs/GaAs/ALGaAs structures by the electrochemical capacitance-voltage technique

In pHEMT devices, a two dimensional (2D) conducting channel representing a quantum well (QW) and adjacent layers of wide-gap semiconductors are fabricated on an undoped material which provides a high mobility of free carriers in the channel. During the development of pHEMT structures it is always very important to estimate and control the free charge carriers concentration, that is not a trivial task because of its redistribution which causes changing of the electric field distribution and, respectively, the energy spectrum of states in the 2DEG channel. By using the modern ECV technique, the pHEMT InGaAs/GaAs/AlGaAs structures were investigated. Free charge carriers concentration profiles were obtained, and the location of 6-layers and the carrier concentration in the QW were estimated.