Space-Charge-Limited Current in Germanium

Citation

Shumka, Alex (1964) Space-Charge-Limited Current in Germanium. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/EV7W-8D66. https://resolver.caltech.edu/CaltechETD:etd-10082002-102055

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. An experimental verification of the theory of space-charge-limited hole current in germanium is presented. Alloyed p-np solid-state diodes of various base widths W are fabricated. The V-I characteristic of each diode is measured at an ambient temperature of 78[degrees]K. These results are compared with theory. Dacey (4) predicts: J = 1.43[epsilon][epsilon][subscript omikron] [mu][subscript omikron] E[subscript c][superscript 1/2]V[superscript 3/2]W[superscript -5/2] where [mu][subscript omikron] is the low field mobility of the holes and E[subscript c] is the critical electric field. This expression assumes a field dependence of hole mobility of [mu] = [mu][subscript omikron](E[subscript c]/E)[superscript 1/2]. The three halves power relationship between current and voltage is observed over nearly two current decades. In that same current range, a direct proportionality of V with W[superscript 5/3] at a constant current density is also observed to within the accuracy of base width and area measurements which are better than 5%. The value of the critical electric field obtained agrees with that estimated by Shockley's model (11). Measurements are also made at higher ambient temperatures. The current decreases as expected from hot carrier considerations. These results represent the first detailed verification of the validity of the theory of pure space-charge-limited current of hot carriers in solids. The measured peak current density of 180 a/cm[superscript 2] is greater than any value reported on space-charge-limited current in solids by an order of magnitude. Photographic materials on pp. 39, 40, 68, 89 and 91 are essential and will not reproduce clearly on Xerox copies. Photographic copies should be ordered.

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