Inverse parabolic quantum wells grown by molecular-beam epitaxy using digital and analog techniques

An ${\mathrm{Al}}_{0.36}$${\mathrm{Ga}}_{0.64}$As/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As inverse parabolic quantum-well structure was grown by molecular-beam epitaxy using both digital and analog compositional grading techniques. Photoluminescence and photocurrent measurements showed distinct exciton peaks for both types of wells. A large Stark shift was found for the digital well, in agreement with the calculations. An observed deviation for the analog well was ascribed to fluctuation in quantum-well parameters. Finally, advantages and disadvantages of the two growth techniques are discussed.