A comparison of electrochemical capacitance-voltage measurements with numerical simulations for pseudomorphic high electron mobility transistor structures

• Published in: Journal of applied physics Vol. 78; no. 4; pp. 2531 - 2536
• Main Authors: Jogai, B., Stutz, C. E.
• Format: Journal Article
• Language: English
• Published: 15.08.1995
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.360108

Electrochemical capacitance-voltage (EC-V) profiling is simulated numerically and the results compared with EC-V measurements for AlxGa1−xAs/InyGa1−yAs pseudomorphic high electron mobility transistor (p-HEMT) structures. The electrostatic potential is calculated at each etch step by solving the Poisson equation subject to surface pinning. The mobile charge is calculated within the Thomas-Fermi approximation. The calculated potential then forms the basis for the numerical EC-V, enabling the capacitance and apparent electron concentration to be computed. The reconstructed electron distribution has been compared with actual EC-V measurements on actual p–HEMT structures. The results affirm the ability of experimental EC-V to separate detailed features in the electron distribution, such as electrons localized in the δ layer and channel of p–HEMTs. Essentially, the reconstructed electron distribution is a warped version of the true distribution as determined from a self-consistent k⋅p calculation. In δ-doped p–HEMTs, for example, the separation between the charges in the δ layer and channel is less than the actual separation. This trend appears to agree with measured EC-V results. Subject to control over the etching uniformity, experimental EC-V should be capable of delineating detailed features in the electron distribution. Numerical EC-V has also been compared with standard capacitance-voltage (C-V) profiling. The reconstructed numerical C-V electron distribution agrees well with the numerical EC-V distribution.