STUDY OF PARTIAL STRAIN RELEASE AND SURFACE-STATES FORMED ON THE SIDEWALL OF INGAAS QUANTUM-WELL WIRES

Strained InGaAs/GaAs quantum-well wires (QWWs) with a lateral wire width of 105 nm and a pitch of 230 nm have been fabricated by holographic lithography and low-damage wet chemical etching. Partial strain release occurs on the sidewalls of the etched QWWs. The photoluminescence spectrum shows two well-resolved excitonic peaks for the QWWs; the lower-energy peak corresponds to the transition from the area close to the sidewall of the QWW and the higher-energy peak is from the center of the QWW. The expected band structure has been modeled, hence expected luminescence spectrum, solving both continuum elasticity equations as well as the four-band Luttinger Hamiltonian with strain. The etched QWWs were given different chemical treatments to test the sensitivity of both excitonic peaks to the quality of the sidewalls. It was found that the lower-energy peak is sensitive to the surface states formed on the sidewalls of QWWs. This sensitivity is believed to be useful in determining the best cleaning and low-damage treatments for subsequent regrowth steps.