Unintentional incorporation of hydrogen in wurtzite InN with different surface orientations

Abstract

We have studied hydrogen impurities and related structural properties in state-of-the-art wurtzite InN films with polar, nonpolar, and semipolar surface orientations. The effects of thermal annealing and chemical treatment on the incorporation and stability of H are also discussed. The near-surface and bulk hydrogen concentrations in the as-grown films increase when changing the surface orientation from (0001) to (000 1) to (1 101) and to (11 20), which may be associated with a decrease in the grain size and change of the growth mode from 2D to 3D. Thermal annealing at 350 o C in N 2 leads to a reduction of H concentrations and the intrinsic levels of bulk H are found to correlate with the structural quality and defects in the annealed films.

Effect of Mg doping on the structural and free-charge carrier properties of InN films

“…The results in Fig. 6(h) 60 We therefore speculate that Mg incorporation leads to the generation of stacking faults and after a critical concentration of Mg ([Mg] ¼ 1.8 Â 10 20 cm À3 for the samples from set A), the density of SFs is sufficiently high that ZB InN inclusions start to form.…”

“…Indeed in our previous works we found large H concentrations in InN films grown by MBE under different growth conditions and in different laboratories. 17,60 Very recent works indicate that O may also play an important role for the conductivity in InN:Mg films. 66 The observed increase of the screw dislocation density and the substantial increase of the symmetric and asymmetric RSM broadening [see Figs.…”

Exciton localization in polar and semipolar (112̅2) In0.2Ga0.8N/GaN multiple quantum wells

“…However, both samples B and C have much smaller IQE values than sample A (table 2), despite the comparable or lower TDD (table 1). The likely reason for this is higher concentrations of unintentional impurities and point defects [14,28] as well as the anisotropic growth of the (112̅ 2) MQW samples (figure 2). Thus, a suppression of these concentrations and an optimized growth condition are believed to have potentiality to strongly enhance the luminescence efficiency of (112̅ 2) nitrides.…”

“…In fact, the O-impurity concentration in (112̅ 2) GaN has been found to be about 1-2 orders of magnitude higher than in polar GaN [14]. Additionally, InN epilayers grown with different surface orientations show a trend in that the H-impurity concentration according to (112̅ 0) > (101̅ 1) > (0001̅ ) > (0001) [28].…”

“…N-polarity) have higher V III and (e.g. O-, H-)impurity concentrations than group-III-polar materials [14,17,28]. It should be noted that non-/semi-polar nitrides have a quasi-N-terminated surface [29].…”