Effect of Hydrogen and Nitrogen Carrier Gas Ratio on the Structural and Optical Properties of AlInGaN Alloy

Undoped AlInGaN epilayers on GaN templates with different hydrogen(H_(2))and nitrogen(N_(2))carrier gas ratios(1:8,2:8,and 3:8 as samples 1,2 and 3,respectively)were grown.When the flow ratio of H_(2) and N_(2) rises from 1:8 to 3:8,an indium composition decrease from 3%to 1.2%is observed while the aluminum content stays constant at any flow ratio.Due to the quantum-dot-like effect,photoluminescence intensity is enhanced in the sample with the low carrier gas flow ratio of H_(2)/N_(2).However,the potential well caused by indium uneven distribution is nonuniform,which is more severe in the sample with carrier gas flow ratio 1:8.The process of carrier transfer from shallow to deep potential wells would be more difficult to accomplish,resulting in the reduction of the photoluminescence intensity.This is found to be consistent with the carriers'lifetime with the help of time-resolved photoluminescence.

Effect of Stress in GaN/AIInGaN Grown on GaN Templates with Different Stress States

We clarify the effect of the stress in GaN templates on the subsequent AIlnGaN deposition by simply growing 150nm AIInGaN on a 30μm GaN template （sample 1） prepared by hydride vapor phase epitaxy and a 2.3μm thin control GaN template （sample 2） prepared by metalorganic chemical vapor deposition. X-ray diffraction and secondary iron mass spectroscopy measurements reveal the stress states （tensile stress and full relaxed for samples 1 and 2, respectively） and compositions （Al0.169In0.01 Ga0.821N, Al0.171In0.006 Ga0.823N for samples 1 and 2, respectively） of AlInGaN. By carefully eliminating other possible factor, as template surface roughness, it is concluded that different stress states of AlInGaN should stem from different stress states of GaN templates.

Effect of pressure on the semipolar GaN(10-11) growth mode on patterned Si substrates

In this paper, we investigate the effect of pressure on the growth mode of high quality （10-11） GaN using an epi- taxial lateral over growth （ELO） technique by metal organic chemical vapor deposition （MOCVD）. Two pressure growth conditions, high pressure （HP） 1013 mbar and low pressure growth （LP） 500 mbar, are employed during growth. In the high pressure growth conditions, the crystal quality is improved by decreasing the dislocation and stack fault density in the strip connection locations. The room temperature photoluminescence measurement also shows that the light emission intensity increases three times using the HP growth condition compared with that using the LP growth conditions. In the low temperature （77 K） photoluminescence, the defects-related peaks are very obvious in the low pressure growth samples. This result also indicates that the crystal quality is improved using the high pressure growth conditions.

Reduction of Efficiency Droop and Modification of Polarization Fields of InGaN-Based Green Light-Emitting Diodes via Mg-Doping in the Barriers

We demonstrate that the Mg-doping in barriers can partially screen the polarization fields of InGaN-based green light-emitting diodes.The photocurrent spectra show that the Mg-doping samples have smaller polarization fields and the blue shift of the peak with increasing current is observed.The reduction of polarization fields can be attributed to the screening of the impurity holes generated by the Mg atoms in the barriers.The efficiency droop is sensitive to the Mg-doping concentration in barriers,while the sample with Mg concentration of 5×10^(19) cm^(-3) exhibits the lowest efficiency degradation of 12.4%at a high injection current.

Effects of the p-AlInGaN/GaN superlattices' structure on the performance of blue LEDs

The advantages of the p-AIInGaN/GaN superlattices＇ （SLs） structure as an electron blocking layer （EBL） for InGaN blue light-emitting diodes （LEDs） were studied by experiment and APSYS simulation. Elec- troluminescence （EL） measurement results show that the LEDs with the p-AllnGaN/GaN SLs＇ structure EBL ex- hibited better optical performance compared with the conventional A1GaN EBL due to the enhancement of hole concentration and hole carrier transport efficiency, and the confinement of electrons＇ overflow between multiple quantum-wells （MQWs） and EBL.