Minority carrier diffusion length and lifetime in GaN

Abstract

Electron beam induced current measurements on planar Schottky diodes on undoped GaN grown by metalorganic chemical vapor deposition are reported. The minority carrier diffusion length of 0.28 μm has been measured, indicating minority carrier lifetime of 6.5 ns. The tapping mode atomic force microscopy imaging of the surfaces and scanning electron microscopy of the cross sections have been used to characterize the linear dislocations and columnar structure of the GaN. The possible influence of recombination on the extended defects in GaN on the minority carrier diffusion length and lifetime is discussed, and contrasted to other recombination mechanisms.

Electron diffusion length and lifetime in p -type GaN

“…Our measurements for electrons in p-type GaN indicated minority carrier lifetimes approximately two orders of magnitude smaller than the observed value for holes in n-type GaN. 7 Since a large concentration of Mg atoms is required to achieve p-type doping ͑due to the relatively deep Mg acceptor level͒, and since trapping lifetimes are inversely proportional to the number of traps, trapping at Mg atoms can explain why the electron lifetime is two orders of magnitude smaller than hole lifetime measured in n-type GaN. 7 The recombination at linear dislocations is another possibility already discussed in case of n-GaN and hole lifetimes.…”

“…7 Since a large concentration of Mg atoms is required to achieve p-type doping ͑due to the relatively deep Mg acceptor level͒, and since trapping lifetimes are inversely proportional to the number of traps, trapping at Mg atoms can explain why the electron lifetime is two orders of magnitude smaller than hole lifetime measured in n-type GaN. 7 The recombination at linear dislocations is another possibility already discussed in case of n-GaN and hole lifetimes. 7 We performed extensive structural characterization of the surfaces of GaN samples analyzed here using atomic force microscopy ͑AFM͒ to establish the possible effects that linear dislocations and other defects may have on transport properties.…”

“…7 The recombination at linear dislocations is another possibility already discussed in case of n-GaN and hole lifetimes. 7 We performed extensive structural characterization of the surfaces of GaN samples analyzed here using atomic force microscopy ͑AFM͒ to establish the possible effects that linear dislocations and other defects may have on transport properties. Linear dislocations are known to induce pits on the surface which can be measured by AFM.…”

“…More details of the experimental procedures, as well as electron beam induced current ͑EBIC͒ measurements on n-type samples have been published elesewhere. 3,7 When electrons from the electron beam are injected into the semiconductor near a Schottky contact, generation of electron-hole pairs occurs. Due to the large concentration of holes in p-type sample compared to the generated electron-hole concentra- tion, only electrons are effectively generated, assuming low electron beam currents.…”

Effect of Mg ionization efficiency on performance of Npn AlGaN/GaN heterojunction bipolar transistors

“…The specific contact resistances for both n and p-type materials are also specified according to recent reports with improved characteristics [14][15][16][17]. The Gummel plot from the initial large area HBT previously demonstrated elsewhere [8,9] is adjusted with simulation by using experimental minority carrier mobility and lifetime values resulting from careful analysis of data available in the literature [18][19][20]. Note that measured Hall mobility values at room temperature are considerably lower than those extracted from a theoretical approach [18].…”