Measurements of the Quantum-Confined Conduction Band Energy in the Wetting Layer Surrounding Individual in 0.4 Ga0.6 as Quantum Dots by Cross-Sectional Ballistic Electron Emission Microscopy

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We measured the quantum-confined conduction band minimum (CBM) energy in the wetting layer (WL) around and behind cleaved self-assembled In0.4 Ga0.6 As quantum dots (QDs) using cross-sectional ballistic electron emission microscopy (XBEEM) at room temperature. With the probe tip positioned over a QD, the dependence of the measured CBM energy on the reverse bias confirmed that XBEEM measured the CBM energy in the wetting layer at the backside of the QD and not in the QD itself. Measurements indicated that the CBM of the quantum-confined wetting layer is approximately 90 meV below the GaAs CBM, and that this conduction band offset is not substantially affected by pinning effects at the metal/semiconductor interface. The amplitude of the BEEM current entering a WL was also observed to decrease once the deposited thickness of an In0.4 Ga0.6 As or InAs layer exceeded a certain threshold, consistent with a reduction in the WL thickness after large-scale QD formation takes place. © 2010 The American Physical Society.

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