Layer perfection in ultrathin InAs quantum wells in GaAs(001)

X-ray standing wave (XSW), x-ray diffraction, and photoluminescence (PL) me asurements were used to assess the layer perfection and positions of 1 and 1/2 monolayer (ML) InAs quantum wells buried in GaAs(001). Local structure in the 1-ML films was evaluated using x-ray absorption fine structure (XAFS ) measurements. Growth temperature effects were studied in a series of samp les produced by metal organic vapor phase epitaxy (MOVPE) between 400 and 6 00 degrees C. The XSW coherent position of the In atoms decreases With incr easing temperature in the 1-ML samples, and the optimal growth temperature is near 550 degrees C, as evidenced by the coherent position of 1.15 +/- 0. 02 and the relatively high coherent fraction of 0.72 +/- 0.08. With decreas ing growth temperature the XSW measurements may suggest segregation of In a toms, which results in an incorporation of the In into multiple layers. The segregation appears to be reduced at the higher temperatures due to the fa vorable kinetic conditions created in the MOVPE environment. Low-temperatur e PL measurements indicate that the sharpest and most intense In-excitonic emission is obtained from the 1-ML sample grown at 530 degrees C. For the 1 /2-ML samples, growth temperatures of 400 and 600 degrees C produce similar standing wave results, although the PL reveals the higher temperature samp le to be of far superior quality, due to excessive carbon incorporation at 400 degrees C. In-As bond-length distortions found in the XAFS measurements agree with a macroscopic elastic description of the pseudomorphic epitaxy.