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Some Details of Publications on this Important Topic
Author -

When quoting text or data from here, please state the reference as
D W Palmer,, 2005.01e (original date of this presentation of the data shown).

The accepted concensus now is that the energy band-gap of InN is about 0.7eV
(see especially the data given below from Arnaudov et al 2004)
rather than the earlier value of about 1.4eV.
However, there is still some disagreement about the interpretation of the experimental data.

Some of the earlier papers that discussed the energy gap value are as follows:

Shubina et et al 2004b
Reply to the Comment by Bechstedt et al 2004

In this reply, these authors said that, because the results of calculations of the band structure of InN depend on the theoretical model employed and on various InN properties assumed in using the model, the arguments given in the Comment by Bechstedt et al 2004 (see below) based on their particular theoretical simulations cannot be considered to be decisive. The reply presents the results of the authors' own simulations of absorption spectra which do not produce a good fit to experimental data in the assumption of a bandgap of less than 1 eV but give a much better fit if a bandgap value of 1.4 eV is assumed. They note that the studies by both them and Bechstedt et al indicate that Mie resonances due to indium precipitates produce peaks in the optical absorption spectrum.

Bechstedt et al 2004
Comment on the paper of Shubina et al 2004a (see below)

The authors of this paper argued that Shubina et al 2004a incorrectly concluded that the observed sharp increase in the optical absorption near 1.4 eV is due to a direct band-gap of that magnitude, and that, instead, that sharp increase arises from an effect of the non-parabolicity of the InN band structure around the Gamma point upon the dielectric function of the semiconductor. They say also that their own theoretical simulation of the optical absorption of InN containing indium precipitates at a concentration of 2% indicates that the observed absorption spectrum is consistent with a direct gap of less than 1 eV together with absorption near 1 eV due to the indium inclusions.

Mahboob et al 2004
DFT-LDA Calculation whose Result is a Value of 0.58eV for the Energy Gap of Hexagonal InN

In conjunction with an experimental investigation of electron accumulation at clean (0001) surfaces of wurtzite InN, this paper reported a theoretical study of the energy band structure of that semiconductor using density-functional theory in the local density approximation. When the pseudopotential used in the calculation was one that included self-interaction corrections for the In 4d electrons, the calculated band structure indicated a direct energy-gap value of 0.58 eV. It seems to the present reviewer, D W Palmer, that the authors present that calculation as a more accurate version of the one reported by Davydov et al in 2002 (see below) which gave an energy gap value of approximately 1.1 eV for wurtzite InN.

Shubina et al 2004a
Experimental Data that indicate an Energy Gap of close to 1.4eV for InN

This paper reported experimental data, obtained by photo-luminescence, cathodo-luminescence, transmission electron microscopy and thermally detected optical absorption (TDOA) on MBE-grown and MOCVD-grown hexagaonal InN, that the authors interpreted as indicating that the well known PL emission from InN at about 0.7eV is due to a transition (a Mie resonance) at an electronic state at the interface between metallic indium inclusions and the InN matrix, and that the actual energy band-gap of hexagaonal InN, as determined from their TDOA data, is close to 1.4eV.

Arnaudov et al 2004
Near-Band-Edge Emission from InN Epitaxial Layers having Different Doping Levels that indicate an Energy Gap of 0.69eV

From analysis of the shape and position of the near-band-edge photo-luminescence from InN having different doping levels, the authors deduced the fundamental energy gap of InN as 0.692±0.002 eV at 2K for an electron effective mass of 0.042m0 at the cb minimum.

Butcher et al 2003
Consideration of the 0.7 PL Emission from InN

This paper proposed that the InN 0.7eV photo-luminescence, previously assigned corresponding to the fundamental cb to vb energy gap, is due, instead, to an electronic transition in a deep carrier trap having \ s> symmetry.

Matsuoka et al 2002
In(x)Ga(1-x)N at Room Temperature for x = 1.0, ie for InN

In experimental studies at room temperature on MOVPE-grown wurzite InN, Matsuoka et al, 2002, found strong photo-luminescence at 0.76 eV and definite optical absorption at 0.7-1.0 eV;   they deduced that the energy gap of wurzite InN is in the range 0.7-1.0 eV, that conclusion being consistent with the 0.7-0.8 eV value proposed by Wu et al 2002 (see below).

Wu et al 2002
In(x)Ga(1-x)N at 77-300 K for x = 1.0, ie for InN

Using the measurement techniques of optical absorption, photo-luminescence and photo-modulated reflectance applied to MBE-grown wurzite InN at 77K and 300K, Wu et al 2002 deduced an energy gap of 0.7-0.8eV for this semiconductor. That new experimental result was unexpected and surprising since previous studies (see below) had indicated an energy gap of 1.9-2.0 eV for wurzite-structure InN.

Davydov et al 2002
Evidence for a Narrow Fundamental Band Gap in Hexagonal InN

This paper presented data on the optical absorption and photo-luminescence of hexagonal InN that, for the first time, showed a direct energy gap of approximately 0.9 eV, ie much lower than the values of about 1.4 eV reported previously in other work. The paper reported also a calculation using density-functional theory in the local density approximation in which a self-interaction correction was used for the In 4d electrons; this work suggested a theoretical direct energy gap of about 1.1eV, which the paper stated should be considered as being in reasonable agreement with the reported measured value.


RELEVANT REFERENCES including to the papers specified above:

Arnaudov B, Pashkova t, Paskov PP, Magnusson B, Valcheva E, Monemar B, Lu H, Schaff WJ, Amano H and Akasaki I
. . . . 2004: Phys. Rev. B 69 (March 2004) 115216
Bechstedt R, Furthmüller J, Ambacher O and Goldhahn R, 2004: Phys. Rev. Lett. 93 (31 December 2004) 269701
Butcher KSA, Wintrebert-Fouquet M, Chen PPT, Timmers H and Shrestha SK
. . . . 2003: Materials Science in Semiconductor Processing 6 (2003) 351-354
Davydov V Yu, Klochikhin A A, Seisyan R P, Emtsev V V, Ivanov S V, Bechstedt F,
. . . . Furthmüller J, Harima H, Mudryi A V, Aderhold J, Semchinova O and Graul J
. . . . 2002: Phys.Stat.Sol.(b) 229 (2002) R1-R3
Koide Y, Itoh H, Khan MRH, Hiramatsu K, Sawaki N and Akasaki I, 1987, J. Appl. Phys. 61 (1987) 4540
Mahboob I, Veal T D, Piper L F J, McConville C F, Hai Lu, Schaff W J, Furthmüller J and Bechstedt F, 2004: Phys. Rev. B 69 (2004) 201307
Martin R W, O'Donnell K P, Middleton P G and Van der Stricht W, 1999, Appl. Phys. Lett. 74 (1999) 263
Matsuoka T et al 2002: Appl.Phys.Lett. 81 (2002) 1246-1248
Monemar B, 1974, Phys.Rev.B 10 (1974) 676
Nakamura S, 1994, Microelec.J. 25 (1994) 651
Nakumura S and Fasol G, 1997,"The Blue Laser Diode - GaN Based Light Emitters and Lasers" (Springer)
O'Donnell K P, Martin R W, Middleton P G, 1999, Phys. Rev. Lett. 82, 237
O'Donnell K P, Martin R W , White M E, Jacobs K, Van der Stricht W, Demeester P, Vantomme A,
. . . . Wu M F and Mosselmans J F W, 1999/2000,
. . . . MRS Fall Meeting 1999: Mat. Res. Soc. Symp. Vol.595 (2000), W 11.26
O'Donnell K P, Martin R W, Trager-Cowan C, White M E, Esona K, Deatcher C, Middleton P G,
    Jacobs K, Van der Stricht W, Merlet C, Gil B, Vantomme A and Mosselmans J F W, 2000,
. . . .E-MRS Spring Meeting 2000, Strasbourg: to be published in Mat. Sci. Eng. B
Osamura K, Naka S and Murakami Y, 1975: J.Appl.Phys. 46 (1975) 3432
Shubina T V, Ivanov S V, Jmerik V N, Solnyshkov D D, Veshkin V A, Kop'ev P S, Vasson A, Leymarie J, Kavokin A, Amano H,
. . . . Shimono K, Kasic A and Monemar B
. . . . 2004a, Phys. Rev. Lett. 92 (19 March 2004) 117407-1 to 117407-4
Shubina T V, Ivanov S V, Jmerik V N, Kop'ev P S, Vasson A, Leymarie J, Kavokin A, Amano H, Gil B, Briot O and Monemar B,
. . . . 2004b: Phys. Rev. Lett. 93 (31 December 2004) 269702
Tansley T L, Goldys E M, Godlewski M, Zhou B and Zuo H Y, 1997a,
. . . . in "GaN and Related Materials", S J Pearton (Ed.), (Gordon and Breach, 1997) p.233
Wu J, 2002: Appl.Phys.Lett. 80 (2002) 3967-3969

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