Application of photoreflectance spectroscopy to the study of interface roughness in InGaAs/InAlAs heterointerfaces

The achievement of high electrical performance InAlAs/InCaAs high-electron- mobility transistors (HEMTs) grown by metalorganic chemical vapor depositio n, requires the growth of a good quality InGaAs channel/InAlAs spacer inter face, in order to ensure good transport properties in the two-dimensional e lectron gas channel. In this article, the interface quality is evaluated as a function of growth interruption time, using photoreflectance spectroscop y. The experimental and theoretical approach used for this purpose is descr ibed. Layers representative of HEMT designs, namely 250 Angstrom InGaAs sin gle quantum wells between InAlAs layers were used for characterization. The interface roughness is estimated from the broadening of the high order qua ntum confined transitions. The results obtained suggest that the higher the growth interruption time, the smaller the interface roughness. Electrical characterization results indicate good agreement with the trends observed b y photoreflectance. (C) 1998 American Institute of Physics. [S0021-8979(98) 00520-9].