Two-dimensional thermal analysis of thin-film pyroelectric infrared detectors

Abstract

A thermal analysis is a critical part of the design of thin-film pyroelectric infrared detectors. Because of the high thermal conductivity of the silicon substrate, it is necessary to isolate the pyroelectric layer thermally. The isolation is accomplished by either use of a low thermal conductivity insulating layer or a bridge structure. If the heat conduction in the detector is only in the direction normal to the detector surface, the thermal problem can be solved analytically using matrix formalism. A number of studies of this type have been presented in the literature. However, a one-dimensional analysis overestimates the responsivity of the detector because a part of the energy of the impinging radiation diffuses in the lateral direction. An analytical solution of the two-dimensional heat transfer problem is not possible, but solutions can be obtained by finite element methods. Analyses are presented in this paper for both ceramic and polymeric detectors and for both insulating layer and bridge structures.

Key Words:

• thin films
• pyroelectricity
• infrared
• finite element analysis