Pyroelectricity in gallium nitride thin films

Abstract

We report on the measurements of the pyroeffect in wurtzite n-type GaN films deposited over basal plane sapphire substrates. We measured the voltage drop between the contacts while the sample was subjected to the uniform heating or cooling. The pyroelectric voltage coefficient extracted from our data is comparable to that of the pyroelectric ceramics (∼104 V/m K). Our results show that the pyroelectric effect in GaN is a combination of a fast response to an initial heat flow and a slower response related to a change in the sample temperature.

Pyroelectric and Piezoelectric Properties of GaN-Based Materials

“…From the experimental data given in Ref. 15 , we estimated P v ~ 10 4 V/m-K. This value is close to the values of P v for pyroelectric ceramics, such as PZT and BaTiO 3 .…”

“…2) heating and cooling. 15 The time dependence of the voltage response in the GaN sample under applied temperature gradient is shown in Fig. 2.…”

“…In Reference 15 , we described a model, which describes the time variation of the pyroelectric voltage. This model accounts for both primary and secondary pyroelectric effects.…”

“…The fast response (jumps in Figs. 3, 4) is caused by the initial thermal flow, which is accounted for by the initial condition in the model described in Reference 15 . In the approximation used in 15 , this response is instant.…”

Large Pyroelectric Response from Reactively Sputtered Aluminum Nitride Thin Films

“…8 Recently Bykhovski et al 9 reported experimental observations of pyroelectric response in thin films of gallium nitride that were ϳ10 4 V/m-K. Because AlN has larger piezoelectric coefficients than GaN, it is reasonable to expect, as suggested in Ref. 2 and 7, that the pyroelectric effect might be higher in AlN.…”