The sample considered herein is an annealed low-temperature (LT) molecular beam epitaxially grown GaAs of n-LT-i-p structure with the LT layer grown at 300 °C. Characteristics involving the dominant trap level located at about 0.66 eV below the conduction band are obtained by analyzing the data of the admittance spectroscopy, capacitance–voltage, current–voltage, and frequency-dependent conductance experiments. This trap pins the fermi level of the LT layer and makes the LT layer semi-insulating. In this structure, the level interacts with both the conduction band and the valence band with a hole emission time constant characterized by an activation energy of 0.77 eV and a cross section of 1.1×10-13 cm2. This level is also an effective generation-recombination center when the temperature exceeds 300 K. © 1998 American Institute of Physics.