Trapping characteristics of Te-related centers in GaAs1−xPx

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Abstract
Transient capacitance and photocapacitance techniques have been used to study the characteristics of two electron traps related to Te in GaAs1−xPx: Te. Levels En1 and En2 have thermal activation energies of 0.17 and 0.27 eV, respectively, and their thermal electron emission and capture rates deviate markedly from Schockley–Read–Hall theory for near band gap crossover compositions. Such centers are found for 0.3<x≤1, are linked to the X conduction band minima, and their photoionization thresholds are 0.5 and 1 eV, respectively. Trap concentrations have been studied as a function of Te doping level, Zn diffusion temperature, and N content (x>0.4) in GaAsP LEDs. It is suggested that both defects belong to the DX type, and they have been described by a large lattice relaxation model. Franck–Condon energies of 0.3 and 0.95 eV have been determined, respectively. The properties of present Te‐related defects are quite similar to donor related centers in AlxGa1−xAs, including the nonexponential capacitance transients found in near x∼0.4 compositions. It is important to mention that both centers have very large hole capture coefficients (σp>10−14 cm2) and behave as efficient recombination centers.