Effects of electron concentration on the optical absorption edge of InN

Wu, Junqiao; Walukiewicz, W.; Li, S. X.; Armitage, R.; Ho, Johnny C.; Weber, E. R.; Häller, E. E.; Lu, Hai; Schaff, William J.; Barcz, A.; Jakieła, R.

doi:10.1063/1.1704853

Cited by 231 publications

(147 citation statements)

References 19 publications

(11 reference statements)

Supporting

Mentioning

131

Contrasting

Unclassified

Order By: Relevance

“…The large E g,opt in sputtered InN samples has been widely discussed in the literature and is generally attributed to its polycrystalline nature and the Burstein-Moss effect associated to their high residual carrier concentration. From our measurement of E g, opt , the free carrier concentration is estimated to be in the range of mid-10 20 cm À 3 [37], in agreement with the residual carrier concentration obtained through Hall measurements in similar InN compact samples deposited by RF sputtering [23]. Fig.…”

Section: Resultssupporting

confidence: 68%

Morphology and arrangement of InN nanocolumns deposited by radio-frequency sputtering: Effect of the buffer layer

Monteagudo-Lerma

Valdueza-Felip

Núñez-Cascajero

et al. 2016

Journal of Crystal Growth

View full text Add to dashboard Cite

a b s t r a c tWe present the structural and optical properties of (0001)-oriented nanocolumnar films of InN deposited on c-sapphire substrates by radio-frequency reactive sputtering. It is observed that the column density and dimensions are highly dependent on the growth parameters of the buffer layer. We investigate four buffer layers consisting of (i) 30 nm of low-growth-rate InN, (ii) 30 nm of AlN deposited on the unbiased substrate (us), (iii) 30 nm of AlN deposited on the reverse-biased substrate (bs), and (iv) a 60-nm-thick bilayer consisting of 30-nm-thick bs-AlN deposited on top of 30-nm-thick us-AlN. Differences in the layer nucleation process due to the buffer layer induce variations of the column density in the range of (2.5-16) Â 10 9 cm À 2 , and of the column diameter in the range of 87-176 nm. Best results in terms of mosaicity are obtained using the bs-AlN buffer layer, which leads to a full width at half-maximum of the InN(0002) rocking curve of 1.2°. A residual compressive strain is still present in the nanocolumns. All samples exhibit room temperature photoluminescence emission at $ 1.6 eV, and an apparent optical band gap at $ 1.7 eV estimated from linear optical transmittance measurements.

show abstract

Section: Resultssupporting

confidence: 68%

Morphology and arrangement of InN nanocolumns deposited by radio-frequency sputtering: Effect of the buffer layer

Monteagudo-Lerma

Valdueza-Felip

Núñez-Cascajero

et al. 2016

Journal of Crystal Growth

View full text Add to dashboard Cite

show abstract

“…Decreasing free carrier absorption coincides with two impor- tant trends: (1) absorption edge shift from ∼1.4 eV to 1.0 eV, and (2) decreasing carrier density. Such correlation suggests a Burstein-Moss shift 30 causing an increase in the apparent bandgap as a result of conduction band filling. Both stoichiometric and Snrich films had carrier densities 1-2 orders of magnitude higher than their Zn-rich counterparts, consistent with a Burstein-Moss shift.…”

Section: Electrical Propertiesmentioning

confidence: 99%

Combinatorial insights into doping control and transport properties of zinc tin nitride

et al. 2015

View full text Add to dashboard Cite

. Broader ContextThin film photovoltaics (PV), based on materials that absorb light 10-100 times more efficiently than crystalline silicon, has the potential to drive down PV module cost by increasing efficiency and requiring less raw material. Currently, the market for thin film PV is dominated by CdTe and CuIn x Ga 1-x Se 2 technologies, which suffer from concerns of toxicity (Cd) or rarity (Te, In) when considering terawatt-scale deployment. As an alternative to these technologies, researchers have turned to studying new absorber materials that exhibit equivalent light absorbing properties but are comprised of Earth-abundant elements. In this work, we explore the properties of a thin film III-N analog, ZnSnN 2 , that until recently has received little attention in the literature. Classification as a III-N analog is advantageous for PV applications, considering that III-N materials are well-known for their stability. ZnSnN 2 possesses a direct bandgap and large absorption coefficient in a PV-relevant energy range, in addition to being composed of abundant and non-toxic elements. However, a few key optoelectronic properties (e.g. doping control and exact bandgap) of this material are not well understood. If this challenge is addressed, ZnSnN 2 has excellent potential as an absorber material for Earth-abundant thin film PV. AbstractZnSnN 2 is an Earth-abundant semiconductor analogous to the III-Nitrides with potential as a solar absorber due to its direct bandgap, steep absorption onset, and disorder-driven bandgap tunability. Despite these desirable properties, discrepancies in the fundamental bandgap and degenerate n-type carrier density have been prevalent issues in the limited amount of literature available on this material. Using a combinatorial RF co-sputtering approach, we have been able to explore a growth-temperature-composition space for Zn 1+x Sn 1-x N 2 over the ranges 35-340• C and 0.30-0.75 Zn/(Zn+Sn). In this way, we were able to identify an optimal set of deposition parameters for obtaining as-deposited films with wurtzite crystal structure and carrier density as low as 1.8 x 10 18 cm -3 . Films grown at 230• C with Zn/(Zn+Sn) = 0.60 were found to have the largest grain size overall (70 nm diameter on average) while also exhibiting low carrier density (3 x 10 18 cm -3 ) and high mobility (8.3 cm 2

show abstract

“…Hydrogen has also been proposed as a source of conductivity in another novel semiconductor material InN, which is actually similar in many respects to TCOs (see Section 5). In that material, there is currently intense debate over whether hydrogen can be seen as the dominant source of conductivity, whether it is present in sufficient quantities, and whether it remains dominant over native defects over the whole Fermi level range spanned in existing material [113][114][115][116][117][118][119][120][121][122]. Such considerations may be expected to apply to TCO materials as well, and further investigations in this area are still required.…”

Section: Origin Of the Bulk N-type Conductivity?mentioning

confidence: 99%

Conductivity in transparent oxide semiconductors

King

Veal

2011

J. Phys.: Condens. Matter

222

180

View full text Add to dashboard Cite

Abstract. Despite an extensive research effort for over 60 years, an understanding of the origins of conductivity in wide band-gap transparent conducting oxide (TCO) semiconductors remains elusive. While TCOs have already found widespread use in device applications requiring a transparent contact, there are currently enormous efforts to (i) increase the conductivity of existing materials, (ii) identify suitable alternatives, and (iii) attempt to gain semiconductor-engineering levels of control over their carrier density, essential for the incorporation of TCOs into a new generation of multifunctional transparent electronic devices. These efforts, however, are dependent on a microscopic identification of the defects and impurities leading to the high unintentional carrier densities present in these materials. Here, we review recent developments towards such an understanding. While oxygen vacancies are commonly assumed to be the source of the conductivity, there is increasing evidence that this is not a sufficient mechanism to explain the total measured carrier concentrations. In fact, many studies suggest that oxygen vacancies are deep, rather than shallow, donors, and their abundance in as-grown material is also debated. We discuss other potential contributions to the conductivity in TCOs, including other native defects, their complexes, and in particular hydrogen impurities. Convincing theoretical and experimental evidence is presented for the donor nature of hydrogen across a range of TCO materials, and while its stability and the presence of interstitial and substitutional species are still somewhat open questions, it is one of the leading contenders for unintentional conductivity in TCOs. We also review recent work indicating that the surfaces of TCOs can support very high carrier densities, opposite to the case of conventional semiconductors. In thin-film materials/devices and, in particular, nanostructures, the surface can have a large impact on the total conductivity in TCOs. We discuss models that attempt to explain both the bulk and surface conductivity based on features of the bulk band structure common across the TCOs, and compare these materials to other semiconductors. Finally, we briefly consider transparency in these materials, and its interplay with conductivity. Understanding this interplay, as well as the microscopic contenders for the conductivity of these materials, will prove essential to the future design and control of TCO semiconductors, and their implementation into novel multifunctional devices.

show abstract

Effects of electron concentration on the optical absorption edge of InN

Cited by 231 publications

References 19 publications

Morphology and arrangement of InN nanocolumns deposited by radio-frequency sputtering: Effect of the buffer layer

Morphology and arrangement of InN nanocolumns deposited by radio-frequency sputtering: Effect of the buffer layer

Combinatorial insights into doping control and transport properties of zinc tin nitride

Conductivity in transparent oxide semiconductors

Contact Info

Product

Resources

About