Persistent Photoconductivity in GaN

The buildup and decay kinetics of PPC observed in GaN are identical to those of DX centres in AlGaAs materials [18], The PPC buildup kinetics can be described by 

103 s even at room temperature. FIGURE 2 shows an example of PPC in an AlGaN/GaN heterostructure recorded at two different temperatures. 

FIGURE 1 (a) A typical behaviour of persistent photoconductivity (PPC) in Mg-doped p-GaN grown by reactive MBE. (b) The dark conductivity as a function of temperature. The bottom curve (solid circles) represents data taken with the sample cooling down in the dark, while the top curve (open triangles) is for data taken with the sample illuminated at 10 K for about ten minutes and then warming up in the dark. After [5], 

For a non-degenerate carrier distribution, the temperature dependence of the PPC time constant t can be described by 

Photocurrent spectra of a p-type GaN epilayer have also been measured [7], From the onset of photoconductivity spectra, it was suggested that metastable centres at 1.1, 1.40, and 2.04 eV above the valence bandedge were responsible for the PPC in Mg-doped GaN, and that Ga vacancies may be responsible for PPC in n-type GaN [7], The spectral dependence of the optical cross section of the PPC related impurities in n-type epilayers has also been measured and the results are shown in FIGURE 4, from which an optical ionisation energy of about 2.7 eV was obtained [8], The correlation between the 

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A3.5 Time-resolved photoluminescence studies of GaN A3.6 Persistent photoconductivity in GaN A3.7 Electrical transport in wurtzite and zincblende GaN A3.8 Characterisation of III-V nitrides by capacitance transient spectroscopy... 

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