We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

Band parameters for III–V compound semiconductors and their alloys

First-principles calculations have evolved from mere aids in explaining and supporting experiments to powerful tools for predicting new materials and their properties. In the first part of this review we describe the state-of-the-art computational methodology for calculating the structure and energetics of point defects and impurities in semiconductors. We will pay particular attention to computational aspects which are unique to defects or impurities, such as how to deal with charge states and how to describe and interpret transition levels. In the second part of the review we will illustrate these capabilities with examples for defects and impurities in nitride semiconductors. Point defects have traditionally been considered to play a major role in wide-band-gap semiconductors, and first-principles calculations have been particularly helpful in elucidating the issues. Specifically, calculations have shown that the unintentional n-type conductivity that has often been observed in as-grown GaN cannot be a...

First-principles calculations for defects and impurities: Applications to III-nitrides

We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” nitrides (wurtzite and zinc-blende GaN, InN, and AlN, along with their alloys) and (2) “dilute” nitrides (zinc-blende ternaries and quaternaries in which a relatively small fraction of N is added to a host III–V material, e.g., GaAsN and GaInAsN). As in our more general review of III–V semiconductor band parameters [I. Vurgaftman et al., J. Appl. Phys. 89, 5815 (2001)], complete and consistent parameter sets are recommended on the basis of a thorough and critical review of the existing literature. We tabulate the direct and indirect energy gaps, spin-orbit and crystal-field splittings, alloy bowing parameters, electron and hole effective masses, deformation potentials, elastic constants, piezoelectric and spontaneous polarization coefficients, as well as heterostructure band offsets. Temperature an...

Band parameters for nitrogen-containing semiconductors

Gallium nitride (GaN) and its allied binaries InN and AIN as well as their ternary compounds have gained an unprecedented attention due to their wide-ranging applications encompassing green, blue, violet, and ultraviolet (UV) emitters and detectors (in photon ranges inaccessible by other semiconductors) and high-power amplifiers. However, even the best of the three binaries, GaN, contains many structural and point defects caused to a large extent by lattice and stacking mismatch with substrates. These defects notably affect the electrical and optical properties of the host material and can seriously degrade the performance and reliability of devices made based on these nitride semiconductors. Even though GaN broke the long-standing paradigm that high density of dislocations precludes acceptable device performance, point defects have taken the center stage as they exacerbate efforts to increase the efficiency of emitters, increase laser operation lifetime, and lead to anomalies in electronic devices. The p...

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Luminescence properties of defects in GaN

The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation, and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes, and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

Gan : processing, defects, and devices

The fabrication and characterization of metal-semiconductor-metal polarization-sensitive photodetectors based on A-plane GaN grown on R-plane sapphire substrates is reported. These photodetectors take advantage of the in-plane crystal anisotropy, which results in linear dichroism near the band gap energy. The high resistivity of the A-plane GaN material leads to extremely low dark currents. For an optimized finger spacing of 1 μm, dark current density and responsivity at 30 V are 0.3 nA/mm2 and 2 A/W, respectively. A maximum polarization sensitivity ratio of 1.8 was determined. In a differential configuration, the full width at half maximum of the polarization-sensitive region is 8.5 nm.

High responsivity A-plane GaN-based metal-semiconductor-metal photodetectors for polarization-sensitive applications

Schottky barrier photovoltaic detectors have been fabricated on epitaxial lateral overgrown GaN layers. The devices show a responsivity of 130 mA/W, independent of optical power and diode size. Due to the lower defect concentration, an improvement of one order of magnitude in the visible rejection ratio has been observed, in comparison with Schottky barrier detectors on standard GaN layers on sapphire. The device time response is RC limited, and the low capacitance of these devices results in an increased bandwidth (<30 MHz in devices with a diameter of 200 μm). A lower noise equivalent power is also observed, due to the reduced leakage current. Detectivities of 5 × 109 Hz1/2 mW—1 were obtained in devices with a diameter of 400 μm, working at —3.4 V bias.

Schottky Barrier Ultraviolet Photodetectors on Epitaxial Lateral Overgrown GaN

Photoluminescence and Raman spectroscopy have been used to determine composition and strain in pseudomorphic InxGa1-xAs/AlxGa1-yAs quantum wells. Series of MBE-grown samples, comprising bulk-relaxed InxGa1-xAs reference layers and InxGa1-xAs/AlyGa1-yAs quantum wells of different thicknesses, were considered. Photoluminescence transitions in the strained structures were analysed using a semiempirical model including strain and composition effects in the InxGa1-xAs well. The GaAs-like longitudinal optical LO phonon Raman shift allowed an independent strain estimation. The agreement between photoluminescence and Raman results confirms the assumption that there is no relaxation in the wells. The effects of uncertainties in the stress deformation potentials and phonon coefficients on strain determination have been discussed. The authors' results show that photoluminescence is an adequate tool to characterize InGaAs strained layers.

https://iopscience.iop.org/article/10.1088/0268-1242/7/4/021/pdf

Photoluminescence and Raman analysis of strain and composition in InGaAs/AlGaAs pseudomorphic heterostructures

A quantitative assessment of the lattice-mismatch in (001) and (111)B InGaAs/GaAs layers, of several compositions and variable thicknesses, is performed by optical techniques, and compared with determinations of residual strain obtained by double-crystal X-ray diffraction. Nomarski microscopy, photoluminescence, and Raman spectroscopies are used to analyze the surface morphology, material quality, and strain relaxation. The relaxation evolution is discussed for those orientations. The critical layer thickness is estimated, being larger for (111)B. A non-uniform lattice accomodation is revealed by the spatial resolution of microprobe optical studies, where regions of different strain degree are observed in (111) layers. Together with the plastic deformation induced by misfit dislocations for both (001) and (111)B orientations, an elastic relaxation is also deduced from variations of the strain degree with depth, which is related to surface roughness.

Strain diagnosis of (001) and (111) InGaAs layers by optical techniques

Deep level transient spectroscopy (DLTS) is performed in MOCVD α-GaN either doped with two different concentrations of Si or unintentionally doped. Capacitance transients are measured in Schottky diodes made of an Au or Ni rectifying contact and an Al/Ti ohmic contact, both on the top of the samples. Only two peaks are detected in each sample in the energy range from the conduction band edge down to 1.1 eV below it, respectively close to 0.50 and 0.92–1.05 eV, by Fourier Transform DLTS (FTDLTS) with concentrations not exceeding 3×1015 cm−3. These two results testify the high crystalline quality of the samples. The deeper level characteristics depend on the shallow impurity, either Si or the unintentional shallow donor, in deep states which comprise in fact a fine structure not evidenced by FTDLTS. A high resolution DLTS (HRDLTS) method is implemented to resolve this fine structure into several sub-levels which cannot be related to distinct chemical environments. The study of emission and capture kinetics confirms that at least three charge states (+,0,-) are involved. It is concluded that MOCVD α-GaN comprises deep centers which are stabilized in such a form with a concentration in the range of a few 1014–1015 cm−3.

E. Muñoz

Papers

High responsivity A-plane GaN-based metal-semiconductor-metal photodetectors for polarization-sensitive applications

Schottky Barrier Ultraviolet Photodetectors on Epitaxial Lateral Overgrown GaN

Photoluminescence and Raman analysis of strain and composition in InGaAs/AlGaAs pseudomorphic heterostructures

Strain diagnosis of (001) and (111) InGaAs layers by optical techniques

Deep levels in MOCVD n-type hexagonal gallium nitride studied by high resolution deep level transient spectroscopy