Al/MoO₃/ZnPc/Al Broken Gap Tunneling Hybrid Devices Design for IR Laser Sensing and Microwave Filtering

Abstract

Herein the design of broken gap heterojunction devices made of molybdenum trioxide and zinc phthalocyanine coated onto Al substrates are reported. The devices which are prepared by the thermal evaporation technique under vacuum pressure of 10(-5) mbar are observed to exhibit a conduction and valence band offsets of 3.36 and 3.56 eV, respectively. The heterojunction devices are observed to form a subband gap of 0.66 eV between the valence bands edges of p- ZnPc and conduction bands edges of p-MoO3 leading to a p(+)/n(+) heterojunction type. Analysis of the current-voltage characteristics of the devices has shown that it exhibits tunneling diode characteristics with maximum tunneling barriers of width of similar to 45 nm. The device displayed biasing dependent photosensitivity in response to 850 nm laser lights. In addition to its characteristics as MOS device, when it was imposed with ac signals in the frequency domain of 0.01-1.80 GHz, it displayed resonance-antiresonancephenomena accompanied with negative capacitance effect in the studied range of spectra. The analysis of the alternating current (ac) electrical conductivity has shown that the ac conduction is mostly governed by quantum mechanical tunneling assisted with correlated barriers hopping. The laser light photosensitivity, the negative capacitance effect, the capacitance switching within 100 ns and the bandpass characteristics with notch frequency of 1.24 GHz make the Al/MoO3/ZnPc/Al attractive for use as IR sensors, parasitic capacitance cancellers, fast capacitance switches and microwave bandpass filters.