| Summary: | 碩士 === 國立交通大學 === 材料科學與工程系所 === 92 === In this study, we grow GaAs on InGaP by LP-MOCVD. Due to the material property of GaAs/InGaP material system, the InGaAsP intermixing layer formed spontaneously in the interface. This quaternary intermixing layer reduced HBT current gain and etching selectivity. Therefore as GaAs was grown on InGaP, the thinner the InGaAsP layer the better the performance of our devices.
As our experiments were concerned, the after growth of InGaP, GaAs was grown at a lower temperature than that for InGaP. This made the P atoms on the InGaP surface hard to desorb and greatly reduce the thickness of InGaAsP intermixing layer. In addition, the lower desorption rate of P atoms increases the PH3 off time. This reduced the residual PH3 in the reactor chamber dramatically and restrained the formation of InGaAsP layer. Both the data of LT-PL and TEM confirmed the experimental results discussed above.
Finally, we used the optimum conditions to grow an InGaP etching stop layer between GaAs layers. By carrying out the etching process, we found a 20Å InGaP etching stop layer will not be penetrated if the etching time were less than 45 sec. By using our optimum growth conditions, the required thickness of InGaP etching stop layer of GaAs/InGaP material will be greatly reduced.
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