InxGa1-xN （x - 0.04） films are grown by metal organic vapour phase epitaxy. For the samples grown on GaN directly, the relaxation of InGaN happens when its thickness is beyond a critical value. A broad band is observed in the 1 spectrum, and its intensity increases with the increasing degree of relaxation. Secondary ion mass spectrometry measurement rules out the possibility of the broad band originating from impurities in InGaN. The combination of the energy-dispersive X-ray spectra and the cathodeluminescence measurements shows that the origin of the broad band is attributed to the indium composition inhomogeneity caused by the phase separation effect. The measurement results of the tensile-strained sample further demonstrate the conclusions.
A back-illuminated mesa-structure InGaAs/InP charge-compensated uni-traveling-carrier （UTC） photodi- ode （PD） is fabricated, and its saturation characteristics are investigated. The responsivity of the 40-μm- diameter PD is as high as 0.83 A/W, and the direct current （DC） saturation current is up to 275 mA. The 1-dB compression point at the 3-dB cutoff frequency of 9 GHz is measured to be 100 mA, corresponding to an output radio frequency （RF） power of up to 20.1 dBm. According to the calculated electric field distributions in the depleted region under both DC and alternating current （AC） conditions, the saturation of the UTC-PD is cansed hv cnmnlete field screening at high optical iniectinn levels
Blue In0.2Ga0.8N multiple quantum wells （MQWs） with InxGa1-xN （x = 0.01 - 0.04） barriers are grown by metal organic vapour phase epitaxy. The internal quantum efficiencies （IQEs） of these MQWs are studied in a way of temperature-dependent photoluminescenee spectra. Furthermore, a 2-channel Arrhenius model is used to analyse the nonradiative recombination centres （NRCs）. It is found that by adopting the InGaN barrier beneath the lowest well, it is possible to reduce the strain hence the NRCs in InGaN MQWs. By optimizing the thickness and the indium content of the InGaN barriers, the IQEs of InGaN/InGaN MQWs can be increased by about 2.5 times compared with conventional InGaN/GaN MQWs. On the other hand, the incorporation of indium atoms into the intermediate barriers between adjacent wells does not improve IQE obviously. In addition, the indium content of the intermediate barriers should match with that of the lowest barrier to avoid relaxation.
