Method and apparatus for low temperature HEMT-like material test

Details Method and apparatus for low temperature HEMT-like material test Method and apparatus for low temperature HEMT-like material test

1993-07-30

1995-07-18

O'Shea, Sandra L.

Electricity: measuring and testing

Magnetic

With means to create magnetic field to test material

324236, 324719, 324637, G01R 2704

Patent

active

054345057

ABSTRACT:
To screen or test the electrical properties of HEMT-like wafers for their quality, the critical layer qualities of a wafer (16) are evaluated by measuring its conductivity (sigma or s) and mobility (mu or m) at upper and lower temperatures, which need only be sufficiently different as to remove uncertainties in the test data but, in practice, are room and liquid nitrogen temperatures. Novel equations show (1) that the crucial quality or merit factor (n.sub.s) the electron sheet density of two-dimensional electron gas (2DEG), can be determined by measuring the total layer conductivity (sigma or s) at the lower or liquid nitrogen temperature and mobility (mu or m) at the upper or room temperature and (2) by measuring overall layer effective mobility (mu or m) at both room and liquid nitrogen (the upper and lower) temperatures to provide a means to measure the value of the 2DEG density, n.sub.s which has better accuracy then where the temperature of mobility is only made at room temperature.

REFERENCES:
patent: 2859407 (1958-11-01), Henisch
patent: 4000458 (1976-12-01), Miller et al.
patent: 4581576 (1986-04-01), Wang
patent: 4605893 (1986-08-01), Braslau
patent: 4704576 (1987-11-01), Tributsch et al.
patent: 5103182 (1992-04-01), Moslehi
patent: 5260668 (1993-11-01), Mallory et al.

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