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

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...

/pdf/luminescence-properties-of-defects-in-gan-4hjs241x7f.pdf

Luminescence properties of defects in GaN

GaN based HFETs are of tremendous interest in applications requiring high power at microwave frequencies. Although excellent current-voltage (I-V) characteristics and record high output power densities at microwave frequencies have been achieved, the origin of the 2DEG and the factors limiting the output power and reliability of the devices under high power operation remain uncertain. Drain current collapse has been the major obstacle in the development of reliable high power devices. We show that the cause of current collapse is a charging up of a second virtual gate, physically located in the gate drain access region. Due to the large bias voltages present on the device during a microwave power measurement, surface states in the vicinity of the gate trap electrons, thus acting as a negatively charged virtual gate. The maximum current available from a device during a microwave power measurement is limited by the discharging of this virtual gate. Passivated devices located adjacent to unpassivated devices on the same wafer show almost no current collapse, thus demonstrating that proper surface passivation prevents the formation of the virtual gate. The possible mechanisms by which a surface passivant reduces current collapse and the factors affecting reliability and stability of such a passivant are discussed.

The impact of surface states on the DC and RF characteristics of AlGaN/GaN HFETs

The macroscopic nonlinear pyroelectric polarization of wurtzite AlxGa1-xN, InxGa1-xN and AlxIn1-xN ternary compounds (large spontaneous polarization and piezoelectric coupling) dramatically affects the optical and electrical properties of multilayered Al(In)GaN/GaN hetero-, nanostructures and devices, due to the huge built-in electrostatic fields and bound interface charges caused by gradients in polarization at surfaces and heterointerfaces. Models of polarization-induced effects in GaN-based devices so far have assumed that polarization in ternary nitride alloys can be calculated by a linear interpolation between the limiting values of the binary compounds. We present theoretical and experimental evidence that the macroscopic polarization in nitride alloys is a nonlinear function of strain and composition. We have applied these results to interpret experimental data obtained in a number of InGaN/GaN quantum wells?(QWs) as well as AlInN/GaN and AlGaN/GaN transistor structures. We find that the discrepancies between experiment and ab initio theory present so far are almost completely eliminated for the AlGaN/GaN-based heterostructures when the nonlinearity of polarization is accounted for. The realization of undoped lattice-matched AlInN/GaN heterostructures further allows us to prove the existence of a gradient in spontaneous polarization by the experimental observation of two-dimensional electron gases?(2DEGs). The confinement of 2DEGs in InGaN/GaN QWs in combination with the measured Stark shift of excitonic recombination is used to determine the polarization-induced electric fields in nanostructures. To facilitate inclusion of the predicted nonlinear polarization in future simulations, we give an explicit prescription to calculate polarization-induced electric fields and bound interface charges for arbitrary composition in each of the ternary III-N alloys. In addition, the theoretical and experimental results presented here allow a detailed comparison of the predicted electric fields and bound interface charges with the measured Stark shift and the sheet carrier concentration of polarization-induced 2DEGs. This comparison provides an insight into the reliability of the calculated nonlinear piezoelectric and spontaneous polarization of group III nitride ternary alloys.

http://iopscience.iop.org/article/10.1088/0953-8984/14/13/302/pdf

Pyroelectric properties of Al(In)GaN/GaN hetero- and quantum well structures

The characteristic surface morphologies of GaN grown by plasma-assisted molecular beam epitaxy under various growth conditions have been investigated. Three growth regimes (one N stable and two Ga stable) are identified on a surface structure diagram (Ga/N ratio versus substrate temperature). The boundary between the N-stable regime (low Ga/N ratios) and the two Ga-stable regimes (high Ga/N ratios) is determined by the growth rate of the films and is constant over the range of substrate temperatures investigated. The boundary between the two Ga-stable regimes (the Ga-droplet regime and the intermediate regime) is determined by the formation of Ga droplets and has an Arrhenius dependence with substrate temperature. The characteristic morphologies of films grown within each of these regimes are investigated using atomic force microscopy and transmission electron microscopy. N-stable films have rough, heavily pitted morphologies. Films grown within the intermediate phase have areas of flat surface between la...

Control of GaN surface morphologies using plasma-assisted molecular beam epitaxy

The formation of the two-dimensional electron gas (2DEG) in unintentionally doped AlxGa1−xN/GaN (x⩽0.31) heterostructures grown by rf plasma-assisted molecular-beam epitaxy is investigated. Low-temperature electrical-transport measurements revealed that the two-dimensional electron gas density strongly depends on both the thickness of the AlGaN layer and alloy composition. The experimental results agree very well with the theoretical estimates of the polarization-induced 2DEG concentrations. Low-temperature electron mobility was found to be much higher in the structures with lower electron sheet densities. Interface roughness scattering or alloy disorder scattering are proposed to be responsible for this trend. A maximum mobility of 51 700 cm2/V s (T=13 K) was obtained in the Al0.09Ga0.91N/GaN structure with a two-dimensional electron gas density of 2.23×1012 cm−2.

Polarization-induced charge and electron mobility in algan/gan heterostructures grown by plasma-assisted molecular-beam epitaxy

GaN:Mg layers grown by plasma-assisted molecular-beam epitaxy at 650 °C are investigated. Secondary-ion-mass-spectroscopy measurements reveal uniform Mg doping profiles with very sharp boundaries. The amount of incorporated Mg atoms changes approximately linearly with incident Mg flux. Hall measurements on p-type GaN:Mg layers show that about 1%–2% of all Mg atoms are ionized at room temperature. The hole mobility depends strongly on the hole concentration, varying from μp=24 cm2/V s for p=1.8×1017 cm−3 to μp=7.5 cm2/V s for p=1.4×1018 cm−3. GaN p–n diodes with molecular-beam-epitaxy-grown p regions are analyzed using current–voltage measurements.

Mg doping of GaN layers grown by plasma-assisted molecular-beam epitaxy

High quality AlGaN/GaN heterostructures have been grown by radio-frequency plasma-assisted molecular beam epitaxy on n-type GaN templates grown on sapphire by metal organic chemical vapor deposition. The unintentionally doped Al0.12Ga0.88N/GaN heterostructure exhibits a 77 K Hall mobility of 14 500 cm2/Vs and a 12 K mobility of 20 000 cm2/Vs (ns=5.0×1012 cm−2). A room temperature mobility of 1860 cm2/Vs (ns=4.8×1012 cm−2) was calculated for the two-dimensional electron gas channel using a two layer model from the measured mobility for the whole structure (template plus heterostructure). Magnetoresistance measurements at 4.2 K showed well-resolved Shubnikov–de Haas oscillations, which began at 2.6 T.

High mobility two-dimensional electron gas in algan/gan heterostructures grown by plasma-assisted molecular beam epitaxy

An AlxGa1−xN/GaN two-dimensional electron gas structure with x=0.13 deposited by molecular beam epitaxy on a GaN layer grown by organometallic vapor phase epitaxy on a sapphire substrate was characterized. X-ray diffraction maps of asymmetric reciprocal lattice points confirmed that the thin AlGaN layer was coherently strained to the thick GaN layer. Methods for computing the aluminum mole fraction in the AlGaN layer by x-ray diffraction are discussed. Hall effect measurements gave a sheet electron concentration of 5.1×1012 cm−2 and a mobility of 1.9×104 cm2/V s at 10 K. Mobility spectrum analysis showed single-carrier transport and negligible parallel conduction at low temperatures. The sheet carrier concentrations determined from Shubnikov–de Haas magnetoresistance oscillations were in good agreement with the Hall data. The electron effective mass was determined to be 0.215±0.006 m0 based on the temperature dependence of the amplitude of Shubnikov–de Haas oscillations. The quantum lifetime was about one...

E. Haus

Papers

Control of GaN surface morphologies using plasma-assisted molecular beam epitaxy

Polarization-induced charge and electron mobility in algan/gan heterostructures grown by plasma-assisted molecular-beam epitaxy

Mg doping of GaN layers grown by plasma-assisted molecular-beam epitaxy

High mobility two-dimensional electron gas in algan/gan heterostructures grown by plasma-assisted molecular beam epitaxy

Characterization of an AlGaN/GaN two-dimensional electron gas structure