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Infrared Optical Devices of Layered Structure

IP.com Disclosure Number: IPCOM000089396D
Original Publication Date: 1977-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 45K

Publishing Venue

IBM

Related People

Chang, LL: AUTHOR [+3]

Abstract

Optical devices in the infrared (IR) wavelength region may be constructed where their operation is based on a characteristic of intraband absorption, resulting from a structure that consists of one-dimensional potential wells.

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Infrared Optical Devices of Layered Structure

Optical devices in the infrared (IR) wavelength region may be constructed where their operation is based on a characteristic of intraband absorption, resulting from a structure that consists of one-dimensional potential wells.

Fig.1 shows a segment of the potential profile with a well width, w, typically of 20-200 Angstroms. The energy states in the x-direction become quantized, E(l) (l = 1,2, ...), but remain continuous in the y, z-direction, as illustrated in Fig. 2. The Fermi level is shown in the lowest band (l = 1), with allowed optical dipole transitions to higher bands (l = even) indicated by arrows. The feature of importance is the parallelness of the bands, leading to a singular joint density of states. The absorption coefficient upon radiation of energy h Nu and polarization along x is given by Alpha = [k/w/2/m/2/ Nu] [l/2// (l/2/ - 1)/2/] [N/Gamma] for E(l) - E(1) - Gamma over 2 < h Nu < E(l) - E(1) + Gamma over 2, and Alpha = 0 where K is a constant, m the electron mass, N the electron concentration, and Gamma the width of the quantum states due to broadening effects such as lifetime and well-to-well interactions.

Fig. 3 plots on a logarithmic scale the calculated absorption coefficient using N = 5 x 10/17/ cm/-3/, W = 100 Angstroms, a barrier height of 0.03 eV, a barrier width of 50 Angstroms and an electron mass of 0.55 m(o). The strength of absorption of the E(1) to E(2) transition is comparable to that of direct interband transition, far exceeding that of typical impurity band absorption. In other words, the present structure has a sensitivity in the far IR region. This property, coupled with that of extreme selectivity in frequency, makes this structure an ultrasensitive detector with high spectral resolution.

Such a one-dimensional potential structure can be realized, for example, by molecular-beam deposition of alternating semiconductor layers, such as GaAs and Ga(...