The aforementioned epitaxy is due to the similarity of hexagonal close-packed sublattices between oxygen on a (111) γ-Al2O3 plane and nitrogen on a (0001) GaN plane. The SAED patterns additionally include spots that are specific to triaxially tripled γ-Al2O3. Selected area electron diffraction (SAED) patterns demonstrate that the crystallized films consist of twinned (111)-oriented cubic γ-Al2O3 with an epitaxial relation of Al2O3 ⟨ 0 1 ¯ 1 ⟩ ∥ GaN ⟨ 2 1 ¯ 1 ¯ 0 ⟩. This current reduction is caused by the enhancement of conduction band offset from 1.4 to 1.8 eV, as revealed by the space-charge-controlled field emission analysis. It is shown that the process of “surface transfer doping” involving an adsorbed water film on the semiconductor surface is likely responsible for the universal alignment of oxygen levels.Īs previously reported, postdeposition annealing at 800 ☌ and higher simultaneously crystallizes atomic-layer-deposited (ALD) Al2O3 films and reduces the current in Al/ALD-Al2O3/(0001) GaN capacitors by two orders of magnitude. Similarly, the results show that the energy of substitutional bulk O-related amphoteric defects incorporated during the crystal growth also has a universal energy of ∼−5.0 eV with respect to the vacuum level for most semiconductors investigated. It is shown here, through the analysis of the reported surface work function values and substitutional bulk O-defect energies, that the surface Fermi level of semiconductors with physisorbed O2 lies universally at approximately −5.1 eV below the vacuum level.
![electron affinity chart electron affinity chart](https://i.ytimg.com/vi/7q8GoAdPBgM/maxresdefault.jpg)
Therefore, a deeper understanding of the interaction of these species with the semiconductor surface and bulk defects is necessary for enabling the development of devices based on them, such as photovoltaic and photocatalytic systems and fuel cells.
![electron affinity chart electron affinity chart](https://1.bp.blogspot.com/-pj76mUXokjI/X74DaEQabrI/AAAAAAAAAco/FjyWwLfi_hoLPuE7DgDxBuJ2H_Pia0qnwCLcBGAsYHQ/w1200-h630-p-k-no-nu/Periodic%2BTable.jpg)
Oxygen and hydrogen are the two most important impurities in semiconductors because of their ubiquitous presence in growth and device processing environments, and consequently, their incorporation strongly influences electronic and electrical properties. The optical properties also exhibit strong strain dependency at the different transition points. More interestingly, the electronic transitions, such as direct to indirect and semiconducting to metallic, are noticed with strain in the considered monolayers. InN, GaN, and AlN monolayers can sustain up to 4%, 16%, and 18% tensile strain, respectively. Further, the III-nitride monolayers are more robust with the tensile strain. These monolayers are more sensitive to compressive strains, showing thermodynamic instability even at 1% compressive strain for all the considered monolayers. The thermodynamic stability of strained monolayers is investigated to explore the maximum possible strains, i.e., flexibility limit, these monolayers can sustain. The biaxial tensile and compressive strains are used as external stimuli to understand their impact on the optoelectronic properties of these monolayers. Electronic properties are computed using the GGA-PBE exchange-correlation potentials, which show the semiconducting behavior with bandgap 0.59 eV, 2.034 eV, and 2.906 eV for InN, GaN, and AlN monolayers, respectively.
![electron affinity chart electron affinity chart](https://image3.slideserve.com/6474399/electron-affinity-l.jpg)
The thermodynamic stability of III-nitride monolayers is calculated using the phonon band structure.