Experimental method for scanning the surface depletion region in nitride based heterostructures

The group-III-nitride semiconductors feature strong spontaneous polarization in the [0001] direction and charges on the respective polar surfaces. Within the resulting surface depletion region the surface field causes band banding and affects the optical transitions in quantum wells. We studied the changes of the emission characteristics of a single GaInN quantum well when its distance to the surface and the influence of the surface field varies. We observe a strong increase of the quantum well emission energy and a decrease of the line width when the surface field partially compensates the piezoelectric field of the quantum well. A scan of the total surface depletion region with a single quantum well as probe was performed. The obtained emission data allow for the direct determination of the width of the depletion region. The experimental method is promising for studies of the surface field and the surface potential of III-nitride surfaces and interfaces. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)