$In_{0.4}Al_{0.6}As$ 버퍼층의 성장온도 변화에 따른 $In_{0.5}Ga_{0.5}As/In_{0.5}Al_{0.5}As$ 다중양자우물(multiple quantum wells, MQWs)의 광학적 특성을 포토루미네션스(photoluminescence, PL)와 시간분해 포토루미네션스(time-resolved PL, TRPL) 측정을 이용하여 분석하였다. $In_{0.4}Al_{0.6}As$ 버퍼층은 기판의 온도를 $320^{circ}C$에서 $580^{circ}C$까지 다양하게 변화시키며 $1{mu}m$ 성장하였으며, 그 위에 $In_{0.5}Al_{0.5}As$ 층을 $480^{circ}C$에서 $1{mu}m$ 성장한 후 InGaAs/InAlAs MQWs을 성장하였다. MQWs는 6-nm, 4-nm, 그리고 2.5-nm 두께의 $In_{0.5}Ga_{0.5}As$ 양자우물과 10-nm 두께의 $In_{0.5}Al_{0.5}As$ 장벽으로 이루어졌다. 4-nm QW과 6-nm QW로부터 PL 피크가 나타났으나, $In_{0.4}Al_{0.6}As$ 성장온도 변화가 가장 큰($320^{circ}C$에서 $580^{circ}C$까지 변화) 시료는 6-nm QW에서의 PL 피크만 나타났다. 낮은 온도($320^{circ}C$에서 $480^{circ}C$까지 변화)에서 성장한 $In_{0.4}Al_{0.6}As$ 버퍼층 위에 성장한 MQWs의 PL 특성이 우수하게 나타났다. 발광파장에 따른 TRPL 결과로 4-nm QW과 6-nm QW에서의 캐리어 소멸시간을 얻었다.
The luminescence properties of $In_{0.5}Ga_{0.5}As/In_{0.5}Al_{0.5}As$ multiple quantum wells (MQWs) grown on $In_{0.4}Al_{0.6}As$ buffer layer have been investigated by using photoluminescence (PL) and time-resolved PL measurements. A 1-${mu}m$-thick $In_{0.4}Al_{0.6}As$ buffer layers were deposited at various temperatures from $320^{circ}C$ to $580^{circ}C$ on a 500-nm-thick GaAs layer, and then 1-${mu}m$-thick $In_{0.5}Al_{0.5}As$ layers were deposited at $480^{circ}C$, followed by the deposition of the InGaAs/InAlAs MQWs. In order to study the effects of $In_{0.4}Al_{0.6}As$ layer on the optical properties of the MQWs, four different temperature sequences are used for the growth of $In_{0.4}Al_{0.6}As$ buffer layer. The MQWs consist of three $In_{0.5}Al_{0.5}As$ wells with different well thicknesses (2.5-nm, 4.0-nm, and 6.0-nm-thick) and 10-nm-thick $In_{0.5}Al_{0.5}As$ barriers. The PL peaks from 4-nm QW and 6-nm QW were observed. However, for the MQWs on the $In_{0.4}Al_{0.6}As$ layer grown by using the largest growth temperature variation (320-$580^{circ}C$), the PL spectrum only showed a PL peak from 6-nm QW. The carrier decay times in the 4-nm QW and 6-nm QW were measured from the emission wavelength dependence of PL decay. These results indicated that the growth temperatures of $In_{0.4}Al_{0.6}As$ layer affect the optical properties of the MQWs.
