Basic Physical Properties of InN

In the absence of good quality single crystal samples, the physical properties of indium nitride have been measured on non-ideal thin films, typically ordered polycrystalline material with crystallites in the 50 nm to 500 nm range. Structural, mechanical and thermal properties have only been reported for epitaxial films on non-lattice-matched substrates. 

Material not grown under ultra high vacuum conditions is susceptible to high levels of oxygen incorporation which may affect physical properties few workers report measured concentrations of this impurity when describing other properties. 

Basic data on the physical properties of indium nitride are sparse and the following sections include instances of values uncorroborated by repeated measurement. In cases where data are absent, the chemical trends across the nitride group have made it possible for first-order estimates to be made and these are included where thought appropriate. The reader is invited to consider these extrapolations by consulting firmer values for AIN and GaN elsewhere in this volume more firmly established data await the advent of better quality material. 

TABLE 1 lists values [1,2,5-10] of basal and perpendicular axes a and c . Note that references [5-10] offer consistent ratios of co/a0 of about 1.615 0.008 and that the ratio approaches the ideal theoretical value of 1.633 only in the case of growth with precautions taken to reduce N vacancies [8]. It is also noteworthy that, amongst data where co/a0 values are close to 1.633 [5-10], values of a0 are also mutually consistent (within about 0.1%) while uncertainties in Co are about ten times greater. This may be attributable to nitrogen deficiency, since N atoms are close packed in (0001) planes and high vacancy densities may preferentially shrink the lattice in the perpendicular direction, parallel to Co. 

The single reported measurement of a0 in the cubic polytype [2] yields a molecular cell volume (a3o/4) of 30.9 A3, compared to 31.2 0.2 A3 [5-10] for the cell volume of the hexagonal polytype  

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A4.3 Basic physical properties of InN TABLE 1 Lattice parameters of indium nitride. 

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