Growth of N-polar In-rich InAlN by metal organic chemical vapor deposition on on- and off-axis sapphire

Metal organic chemical vapor deposition is used to grow N-polar In-rich InAlN layers directly on on-and off-axis (misoriented by 4 degrees towards a plane) c-plane sapphire substrates. During the InAlN growth, trimethylaluminum, ammonia, and the total flow was kept at 4.74 mu mol/min, 3 slm and 10 slm, respectively, while trimethylindium (TMIn) flow was selected between 8.42 and 13.48 mu mol/min. All samples were grown at about 706 degrees C however; TMIn flow of 10.95 mu mol/min was also tested at the growth temperature of 686 degrees C. With increasing the TMIn flow, the In molar fraction increased from 0.55 to 0.69, irrespectively of the substrate miscut. For the moderate TMIn flow and In molar fraction of less than 0.63, density of screw and edge dislocations were from 0.3 to 12 X 10(9) cm(-2) and 5 to 7 X 10(10) cm(-2), respectively, while decisively lower densities appeared on on-axis structures. On the other hand, InAlN surface RMS roughness was from 1 to 8 nm favouring the off-axis substrate and low TMIn flow. Structural and surface deterioration appeared with the highest TMIn flow of 13.48 mu mol/min and In molar fraction of 0.69, which hold also for reduced temperature of the growth. Nevertheless, room temperature pho-toluminescence full-width at half maximum less than 270 meV appeared for all samples, with maxima between 1.9 and 1.5 eV. In-rich N-polar InAlN grown on on-axis sapphire can be used as a buffer layer in new types of heterostructure devices.

Automated summary

Metal organic chemical vapor deposition was used to directly grow N-polar In-rich InAlN layers on on-and off-axis c-plane sapphire substrates. The InAlN layer's composition and surface morphology can be controlled by adjusting the trimethylindium flow. Room temperature photoluminescence shows narrow full-width at half maximum for all samples, indicating the potential of using In-rich N-polar InAlN as a buffer layer in new types of heterostructure devices.