NOVEL STRUCTURE FOR MEASURING THE DENSITY-OF-STATE DISTRIBUTION OF HIGH-RESISTIVITY SEMICONDUCTOR-FILMS BY ISOTHERMAL CAPACITANCE TRANSIENTSPECTROSCOPY

A novel structure, metal/high-resistivity semiconductor (HRS)/n-type c -Si substrate with the space charge region (SCR) entirely covering the HRS film and penetrating into the c-Si substrate, has been proposed f or determining the density-of-state distribution g(E) of the HRS films via the isothermal capacitance transient spectroscopy (ICTS) method. The structure has been tested and applied to the measurement of g(E) o f the undoped hydrogenated amorphous silicon (a-Si:H) film. For undope d a-Si:H film with optical gap E(o) = 1.72 eV, a peak in g(E) is obser ved at 0.66 eV below the conduction band mobility edge E(c), with the attempt-to-escape frequency of u(n) = 1.61 x 10(13) s(-1). These midga p states are surmised to be correlated with the doubly occupied dangli ng bond D-.