Electrical characterization of insulator-semiconductor systems based on graded band gap MBE HgCdTe with atomic layer deposited Al2O3 films for infrared detector passivation

The electrical properties of MIS structures based on graded band gap Hg0.77Cd0.23Te grown by the molecular beam epitaxy method with the Al2O3 dielectric formed by the plasma enhanced atomic layer deposition method were investigated. It is established that for such structures the recharge of slow states takes place and significantly distorts the form of the capacitance-voltage (C-V) characteristics. A technique is proposed for constructing the C-V curves of HgCdTe MIS structures, which makes it possible to eliminate the effect of slow surface states. It is shown that Al2O3 films are suitable for passivation of infrared detectors due to small flat band voltages leading to the realization of the depletion or weak inversion modes. The hysteresis of electrical characteristics is eliminated when an intermediate CdTe layer with a thickness of about 0.2 μm is grown in situ during the epitaxial growth.