Space-charge-limited hole and electron currents in germanium

Properties associated with space-charge-limited (SCL) currents in solids are summarized in terms of their potential for device application. The effect of space-charge on limiting the flow of injected current carriers is investigated in alloyed Ge solid-state diodes. Experimental results are presented for SCL hole currents in near-intrinsic n-type Ge (ν-type) and SCL electron currents in near-intrinsic p-type Ge (π-type). I-V characteristics of p⁺ν p⁺and n⁺π n⁺solid-state diodes of various base widths W are measured at various ambient temperatures (78°K, 195°K, and 273°K). An relation is observed for pure SCL hole and SCL electron currents. Theory predicts an relation and is of the form I=1.43 where µ is the low field mobility and Ecis the critical electric field. A field dependent mobility of is assumed. A good agreement between theory and experiment is obtained. These experimental results indicate that it is practically feasible to obtain SCL current in Ge. The potential application of SCL current in a solid-state triode will be discussed.