Hole transport and carrier lifetime in InN epilayers

Abstract

Time-resolved transient grating spectroscopy has been conducted to measure the ambipolar diffusion coefficient and to derive the hole mobility and carrier lifetime in an InN epilayer simultaneously. The ambipolar diffusion coefficient Da=2.0cm2∕s, hole mobility μh=39cm2∕Vs, and carrier lifetime τR=5.4ns at 300K near the InN surface were determined by monitoring the transient grating kinetics at various grating periods. In addition, we observed a decrease of hole mobility and carrier lifetime at the internal epilayer/buffer interface in comparison with those at the free surface, suggesting a faster carrier capture rate to the defect states and a more efficient defect and impurity scattering mechanism.

High field electron and hole transport in wurtzite InN

“…This value of electron mobility is in agreement with the electron mobility m e ¼ 2100 cm 2 /Vs measured in Ref. [16] at electron density of 3.7 Â 10 17 cm À3 . The calculated peak of electron drift velocity at E ¼ 40 kV/cm is 4.7 Â 10 7 cm/s which corresponds to the high-field drift velocity of (5.1 AE 0.5) Â 10 7 cm/s obtained in Ref.…”

Nonlinear carrier recombination and transport features in highly excited InN layer

“…The best fit to the experimental kinetics was found taking the linear recombination time τ R = 1.5 ns and nonlinear recombination rate 1/τ * R ∝ B * (n 0 +N) with B * = 8×10 -10 cm 3 s -1 . The reciprocal dependence of recombination rate on total carrier density was similar to the contribution of radiative recombination, which also has a relationship B ∝ 1/N, but the high value of the determined coefficient B * was not consistent with the suggested interband recombination rate in InN (B * >> B = 3×10 -11 cm 3 s -1 at 300 K [2,3]). On the other hand, a trap-assisted Auger recombination process, involving two particles where the released energy from trapping is given to a second electron or hole, obeys the same functional dependence as the radiative recombination.…”

“…The latter observation was attributed to Auger recombination process in a degenerated carrier system, for which the relationship 1/τ Aug ∝ N is valid. We note that our study of carrier mobility in highly excited InN provided the minority carrier mobility value, typical for nondegerate electron system at room temperature [3].…”

“…The complementary measurements of carrier lifetime by using time-resolved transient grating technique provided much longer carrier lifetime (5.4 ns) in the sample with the lowest background electron density (3.7×10 17 cm -3 ) [3], in contrary to 1.3 ns value determined from the DT kinetics [1].…”

“…Even at the highest pump fluence of ~0.5 mJ/cm 2 , which created the average carrier density of about 10 19 cm -3 [1], the single exponential decay of DT confirmed the dominant role of the defectrelated non-radiative recombination at 300 K. A contribution of bimolecular recombination was suggested at 20 K, as the measured carrier lifetime (670 ps) was close to the calculated one, taking the radiative recombination coefficient B=2.6×10 -11 cm 3 s -1 value. The complementary measurements of carrier lifetime by using time-resolved transient grating technique provided much longer carrier lifetime (5.4 ns) in the sample with the lowest background electron density (3.7×10 17 cm -3 ) [3], in contrary to 1.3 ns value determined from the DT kinetics [1].…”