Space-Charge-Limited Current of Holes in Silicon and Techniques for Distinguishing Double and Single Injection

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Abstract
Space‐charge‐limited (SCL) current of holes has been observed in high‐resistivity silicon at room temperature through proper sample design and suitable choice of an upper limit for electric fields applied in the sample. Joule heating and hot‐carrier effects, which limited the observation of SCL current in previous work, were hardly noticeable in our measurements. Current—voltage characteristics were measured and found to contain an Ohmic portion followed by a region that obeyed the theoretical space‐charge‐limited‐current law J=(9/8)εμpV2/L3. This behavior has been verified for various samples differing in lengths by a factor of 10. The value of the incremental capacitance of the samples, when suitably corrected for fringing capacitance, was found to agree with the value (¾) C predicted by Shao and Wright for SCL currents, where C is the capacitance due to the sample geometry. Values of current were observed to be much greater on some samples than those predicted by the single carrier space‐charge‐limited‐current law. The excess current was identified with double‐injection behavior. The double injection was caused by a surface condition that allowed electrons to be injected at the negatively biased contact. Comparison with the capacitance—voltage characteristic and transient response behavior of double‐injection structures aided in identifying the nature of the excess current.