Optical studies of MBE-grown InN nanocolumns: Evidence of surface electron accumulation

Understanding the role of Si doping on surface charge and optical properties: Photoluminescence study of intrinsic and Si-doped InN nanowires

“…8,[19][20][21][22][23][24][25][26][27][28][29][30] For example, in general, the currently reported nominally undoped InN is n-type degenerate, with the residual electron densities in the range of ∼ 1 × 10 18 cm −3 , or higher. 8,11,25,[31][32][33][34] Moreover, it has been generally observed that there exists a very high electron concentration (∼ 1 × 10 13−14 cm −2 ) at both the polar and nonpolar grown surfaces of InN films, 19,35 and the Fermi-level (E F ) is pinned deep into the conduction band at the surfaces; 19,20,29,30 similar electron accumulation profile has also been measured at the lateral nonpolar grown surfaces of [0001]-oriented wurtzite InN nanowires. 8,11,21,22,25,36 In this regard, significant efforts have been devoted to understanding the fundamental surface charge properties of InN.…”

“…8,11,25,[31][32][33][34] Moreover, it has been generally observed that there exists a very high electron concentration (∼ 1 × 10 13−14 cm −2 ) at both the polar and nonpolar grown surfaces of InN films, 19,35 and the Fermi-level (E F ) is pinned deep into the conduction band at the surfaces; 19,20,29,30 similar electron accumulation profile has also been measured at the lateral nonpolar grown surfaces of [0001]-oriented wurtzite InN nanowires. 8,11,21,22,25,36 In this regard, significant efforts have been devoted to understanding the fundamental surface charge properties of InN. 20,23,27,29,30,[37][38][39] The electron accumulation at polar InN surface has been explained by the presence of large density of the occupied In-In bond states above the conduction band minimum (CBM), 23 as well as the unusual positioning of the branch point energy (E B ) well above the CBM at the Γ-point, which allows donor-type surface states to exist in the conduction band; 20 for polar InN surface, theoretical studies agree well with experiments.…”

“…7,9,40 Meanwhile, significant efforts have also been made to study the optical properties of InN nanowires. 8,11,21,24,28,33,45 The PL spectra of nominally undoped InN nanowires typically exhibit a very large inhomogeneous broadening, a peak energy considerably larger than the bandgap of InN, as well as an anomalous dependence on temperature. Due to these strong n-type characteristics of nominally undoped InN nanowires, the optical properties of intrinsic InN nanowires, and the dependence on the charge carrier concentrations and surface charge properties had remained not clear.…”

“…InN, after being discovered of a narrow bandgap (E g ∼ 0.65 − 1 eV) [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and predicted to possess the largest electron mobility among group-III nitrides (∼ 4400 cm 2 ·V −1 ·s −1 at 300 K), 15 has emerged as a highly promising material for infrared photodetectors and lasers, solar cells, ultrahigh-speed transistors, and sensors. [16][17][18] To date, however, the practical device applications of InN-based materials have been severely limited by the presence of extremely large residual electron density and the uncontrolled surface charge properties, as well as the difficulty in achieving p-type conductivity.…”

Growth of InN quantum dots to nanorods: a competition between nucleation and growth rates

“…S1). Nanorods are also shown in the TEM studies ( The presence of O at 700 o C may be correlated to its associated dissociation of InN and reoxidation at high growth temperature [7,8] [25,26]. Among these, A 1 and E 1 modes are polar in nature; because of this reason these modes are further split into longitudinal optic (LO) and transverse optic (TO) components.…”