Abstract
Flow of photocurrent through the metal-oxide-semiconductor structure induced by the pulsed infrared CO2 laser is investigated experimentally. In the case of a perfect insulator, the photocurrent has a photocapacitive character. Its rise is based on the hot carrier phenomenon; no carrier generation is present, only redistribution of laser-heated carriers takes place at the semiconductor surface. The magnitude of this displacement current is related to the capacitance of the structure and is dependent on the rate of the laser pulse change as well as on the laser light intensity. This effect can find application in the detection of fast infrared laser pulses as well as in the development of infrared photovaractors. Operation of such devices would not require cryogenic temperatures what is usually needed by the long-wavelength infrared semiconductor technique.
Highlights
Capacitors with optically-variable properties attract research interest due to their potential application in a variety of electronics devices
At reverse voltagei,ohnoles of the p-Si are accumulated at the semiconductor surface, CS incTrehaesmeseaasnudredexCc-eVedchsatrhaectevraislutiecsooff tChie, afanbdrictahteedtoMtaOl ScastpruactiutarnescearoefptrheseensterudcintuFriegugreets2
At reverse voltage, holes of the p-Si are accumulated at the semiconductor surface, CS increases and exceeds the value of Ci, and the total capacitance of the structure gets close to Ci [25]
Summary
Capacitors with optically-variable properties attract research interest due to their potential application in a variety of electronics devices. The hot carrier effect attracts interest from the fundamental point of view but it finds a lot of applications It is employed in the detection of microwave [9,10] and infrared radiation [11], and even within the whole region between both these ranges including the THz frequencies [12,13]. It was assumed that carrier heating causes a change of the barrier capacitance, and this phenomenon was called a photocapacitive effect [24]. In this communication, we report photosignals induced by infrared CO2 laser radiation across an Al-SiO2-p-Si structure. We evidence a laser induced hot carrier photocurrent under conditions when no conduction photocurrent can flow through the insulating layer of the MOS structure
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