Photocurrent decay in n-type GaN thin films

Abstract

Minority carrier relaxation in undoped n-type gallium nitride (GaN) thin films was studied by photoconductivity decay measurements in the time span from 50 ns to 50 s. The decay is characterized by an initial exponential decay followed by a quasi-power-law decay for decades of time longer than 1 μs. The decay rate is insensitive to the electron concentration and is only slightly temperature dependent. The results are discussed in terms of hole trapping at gap states and subsequent recombination. The studies revealed that the dominant recombination mechanism is very different from recombination through dislocations and that the valence band-tail states in n-type GaN seem to be negatively charged.

Photoconductivity in AlxGa1—xN with Different Al Contents

“…The below band gap response extended into the infrared region without any pronounced spectral dependence which would indicate the involvement of specific deep traps, e.g. E1 which is located 200 meV below the conduction band [14,15] similar results were reported in the literature [15,16]. The temperature dependence of the photoconductivity was studied from 4.2 to 500 K. The GaN and AlGaN peak positions shifted to lower energies consistent with the decrease in the band gap energy.…”

A Novel Approach to Semiconductor Electrical Properties - The Advanced Method of Transient Microwave Photoconductivity (AMTMP)

“…TOF experiments on CdTe polycrystalline films [23] showed that ac increased with decreasing temperature. Photocurrent studies of GaN thin films [24] also exhibited the same temperature behavior for a. Therefore, our results for polycrystalline CdSe show the same behavior as these other polycrystalline films, and these results can not be explained satisfactory by the MT model.…”

Observation of optically-active metastable defects in undoped GaN epilayers

“…In fact, the hole traps have been revealed by several groups. [25][26][27] The theoretical calculations showed that the Ga vacancy is normally a triply charged acceptor level. 4,19 Hole capture should be easy in the deep levels.…”