Scanning tunneling microscopy and spectroscopy are used to study InGaPGaAs heterojunctions with InGaAs-like interfaces. Band offsets are probed using conductance spectra, with tip-induced band bending accounted for using three-dimensional electrostatic potential simulations together with a planar computation of the tunnel current. Curve fitting of theory to experiment is performed. Using an InGaP band gap of 1.90eV, which is appropriate to the disordered InGaP alloy, a valence band offset of 0.38±0.01eV is deduced along with the corresponding conduction band offset of 0.10±0.01eV (type I band alignment).

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Specified values of the separation refer to, in all cases, the value at the setpoint (constant current of 0.1nA, at a sample voltage of 2V relative to the tip). As detailed in Sec. II, the separation varies during the spectral measurement according to s=s0+aV, where V is the sample voltage. The values of a are precisely known for each spectrum, and this same s variation is used in the computations.

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For the STM image of Fig. 2(a) a high-order polynomial has been used as a background subtraction, to permit ease of viewing of the data in the grayscale format, whereas for Fig. 8(a) this background subtraction is not performed.

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States with even or odd symmetry relative to the center of the slab are constructed, with periodic boundary conditions across the slab. For each of these types of states have spacing in the wavevector kx0 of 2π. The results of Eqs. (A10a), (A10b), (A11a), and (A11b) are valid for both even and odd parity states.

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