Since there are always some Mg floating on the surface during growth Ku-0059436 molecular weight because of segregation [26], the interruption will drive the floating Mg to incorporate into the Al x Ga1 – x N crystal, thus greatly enhancing Mg solubility. This result confirms that the Mg incorporation on the growing surface

can be transiently enhanced further by an extremely N-rich condition interruption, thereby increasing the C Mg that would reside at the interrupting region. However, the C Mg enhancement at the interruption region is much smaller than that on the final selleck compound epilayer surface (Figure 1c), and the C Mg far from the interruption region remains low. This result is caused by the wide interval between consecutive interruptions, considerably decreasing the C Mg at the interruption regions and resulting in the non-uniformity of the C Mg distribution by Mg segregation and diffusion after interruption (Figure 3a). Therefore, the interruption interval, interruption time, and growth rate should play critical roles in affecting the C Mg overlap. As illustrated in Figure 3b, we further proposed the MSE technique, optimizing the interruption conditions, to incorporate surface Mg atoms

before they MAPK Inhibitor Library can re-segregate to the surface, thus further increasing the average Mg incorporation and approaching a uniform Mg distribution over the entire AlGaN epilayer instead of being distributed locally. Figure 3 Schematic diagram of the Mg incorporation behavior in the AlGaN grown by the MSE technique. As the interruption interval is long, only some peaks distribute locally at the interruptions C1GALT1 after Mg segregation and diffusion (a), optimizing the interruption interval, a high and uniform Mg distribution over the entire AlGaN epilayer could be achieved (b). Three Mg-doped Al x Ga1 – x N (x = 0.54, 0.76, 0.99) samples were grown by using the MSE technique (the inset of Figure 2b). An optimized 2-nm interruption

interval combining with 2-s interruption time were used for all samples, with Cp2Mg flux of 0.81 nmol/min. As shown in Figure 4a, the samples with different Al contents exhibit high C Mg range from 4 × 1019 cm -3 to 5 × 1019 cm -3 and homogeneous distribution at a wide region as expected, whereas the C Mg of the samples grown via conventional method decrease with increasing Al content, which is consistent with the theoretical prediction. By comparison, the average C Mg in the samples with different Al contents increase several times, and the enhancement ratios increase as the Al content increases, as shown in Figure 4b. Particularly, the enhancement ratio is approximately up to 5 in the Al0.99Ga0.01N. These results indicate that a high C Mg can be easily achieved in Al-rich AlGaN by combining the surface effect with the N-rich growth atmosphere modulation. Figure 4 Bulk C Mg of the samples and enhancement ratios of Mg/H concentrations.