Unusual capacitance behavior of quantum well infrared photodetectors

Abstract

We report experimental and simulation results of capacitance of quantum well infrared photodetectors (QWIPs). We found that the QWIP capacitance displays unusual behavior as a function of voltage and frequency, deviating far from the constant geometric capacitance value. At high voltages, capacitance starts with a negative value at low frequencies, increases above zero with frequency, and eventually decays to the geometric capacitance value. The magnitude of negative capacitance exceeds the geometric capacitance by more than two orders of magnitude. Negative capacitance arises when the transient current in response to a voltage step is nonmonotonic with time. Simulation shows that this effect is due to nonequilibrium transient electron injection from the emitter resulting from the properties of the injection barrier and inertia of the QW recharging processes.

Langevin approach to the generation–recombination noise of a multi quantum well infrared photodetector

“…According to the relationships (9), (10), for a given value of the current I, the current noise power spectrum should therefore vary as 1/N and the responsivity should be independent of N. However, deviations of the behavior of the dynamic and static photoresponse [7][8][9][10][11] and of the noise power spectra [26,27] have been reported.…”

“…Despite the relatively simple structure of the QWIPs, the physical processes responsible for their operation is fairly complex [7][8][9][10][11][12][13]. It has been shown that the non-uniformity of the space charge regions over the quantum well periods may affect the QWIPs operation.…”

Zero-bias offsets in the low-temperature dark current of quantum-well infrared photodetectors

“…We propose that the series resistance in this RC circuit is due to tunneling mechanisms (which dominate the dark current at lower temperatures), which in turn are structure-and bias-dependent. The capacitance is a barrier capacitance that can give rise to a quantummechanical separation of charge by the barriers and has been described by Ershov et al 14 The unusual capacitance behavior of QWTPs with frequency and bias has also been observed by Ershov et al 15 We have applied our RC circuit model to several QWEP structures and found that it describes their low-temperature I-V characteristics very well.…”

General mechanism for negative capacitance phenomena

“…It has been observed in samples as different as crystalline and amorphous semiconductor devices, [1][2][3][4][5][6][7][8][9] organic compounds, [10][11][12][13][14] composite materials/nanomaterials, 9,15-22 electrochemical cells, [23][24][25] geological samples, 26 biological membranes, [27][28][29] and even moist surfaces. 30 Furthermore, it has been shown that NCs can originate at interfaces as well as in the bulk of the materials.…”