F. Nakamura

Band lineup for a GaInP/GaAs heterojunction measured by a high‐gain Npn heterojunction bipolar transistor grown by metalorganic chemical vapor deposition

A GaInP(N)/GaAs( p) heterojunction bipolar transistor was fabricated by metalorganic chemical vapor deposition (MOCVD) for the first time. The common‐emitter current gain exceeded 200 at a current density around 10 A/cm2 and the offset voltage was as small as 50 mV. Thermionic emission theory indicates that the conduction‐band discontinuity (ΔEc) at GaInP/GaAs heterointerface is as small as 30 meV at room temperature and this value was more than 160 meV smaller than 0.19–0.22 eV obtained by the C‐V profile method. The band‐gap energy for MOCVD‐grown GaInP was 60 meV smaller than the intrinsic band‐gap energy (1.91 eV), but this value is too small to explain the difference between the present ΔEc value and the previously reported ΔEc value.

Residual strain dependence of optical characteristics in GaN layers grown on (0001) sapphire substrates

GaN layers were grown on (0001) sapphire substrates by metalorganic chemical vapor deposition with various growth conditions. Some samples were grown with pressures higher than atmospheric. The residual strain in the epitaxial layer was estimated by measuring the lattice constants using x-ray diffraction. The optical quality was evaluated in terms of the threshold power density of stimulated emission. The residual strain perpendicular to C face, ezz, ranged from 0.058% to 0.125%. The strain ratio under biaxial stress (Δc/c)/(Δa/a), is estimated to be −0.46 from the relation between the lattice constants a and c. From the photoluminescence spectra with weak excitation, δEA/δezz for undoped GaN is estimated to be 16.4 eV. The threshold power density decreased from 2.77 to 0.59 MW/cm2 as the strain increased, suggesting that the strain relaxation process is accompanied by a generation of defects which act as nonradiative recombination centers.

Blue-green laser diode grown by photo-assisted MOCVD

Abstract Operation of the first blue-green laser diode grown by metalorganic chemical vapor deposition has been demonstrated at 77 K under pulsed current injection. The precursors were dimethylzinc, dimethylcadmium, diethylsulfide, bismethyl-cyclopentadienyl-magnesium, and dimethylselenide. Diisopropylamine and ethyliodide were used for a p-type and n-type doping under irradiation with ultraviolet light generated by a high-pressure mercury lamp, respectively. A 1 × 10 18 cm −3 nitrogen-atom concentration, which was measured by secondary ion mass spectroscopy, was obtained in the p-ZnSe contact layer. The 4.2 K photoluminescence spectrum was dominated by strong donor-acceptor pair emission and the net acceptor concentration was 1.4 × 10 16 cm −3 .

Epitaxial growth of ZnMgTe and double heterostructure of ZnTeZnMgTe on GaAs substrate by metalorganic chemical vapor deposition

Abstract We have epitaxially grown ZnMgTe ternary alloys, whose Mg content is between 0% and 50%, on (100) GaAs substrates by metalorganic chemical vapor deposition. The band-gap energy estimated from the emission wavelength at room temperature can be varied from 2.26 to 2.57 eV. In the photoluminescence (PL) measurements at 4.2 K, band-edge emission was clearly observed up to Mg content of 25%. The refractive index decreases as Mg content increases. In the PL spectra of double heterostructures of ZnTe ZnMgTe at 4.2 K, strong emission and quantum size effect were observed. These results suggest that effective carrier and optical confinement are possible.

Investigation of orientation effect on contact resistance in selectively doped AlGaAs/GaAs heterostructures

We established that the contact resistance to the two‐dimensional electron gas (2DEG) in selectively doped n‐AlGaAs/GaAs heterostructure is crystal orientation dependent. The contact resistance in the [011] direction is the lowest and that in the [011] direction is the highest. The contact resistance monotonically changes between the [011] and [011] directions. We also find the sheet resistance dependence of the contact resistance.

Epitaxial growth of ZnMgSSe on GaAs substrate by metalorganic chemical vapor deposition

Room temperature blue laser action in an optically pumped metalorganic chemical vapor deposition (MOCVD)-grown ZnSe/ZnMgSSe double heterostructure is demonstrated. In the atmospheric pressure metalorganic chemical vapor deposition process, dimethylzinc (DMZn), bismethyl-cyclopentadienyl-magnesium ((MeCp) 2 Mg), diethylsulfide (DES), and dimethylselenium (DMSe) are used as sources. Mirror surface morphology is achieved up to a Mg content of 13% in the ZnMgSSe. Good crystal quality of the ZnMgSSe layer, lattice-matched to GaAs, is indicated by photoluminescence measurement at 4.2 K as well as by X-ray diffraction. The spectrum of photoluminescence is dominated by a sharp near-band-edge emission. The full width at half maximum of the (400) X-ray diffraction peak of Zn 0.95 Mg 0.05 S 0.15 Se 0.85 layer is 170 arc sec

Uniform (Al)GaAs crystal growth and microwave HIFETs grown by barrel-reactor MOCVD

Abstract A barrel-reactor MOCVD system accommodating seven 2 inch wafers was developed. The growth rate uniformity of (Al)GaAs was ±2% in a wafer and ±1% at the same position in seven wafers. An (AlAs)5-(GaAs)2 monolayer-scale superlattice were grown and their structure were verified by Raman scattering and transmission electron microscopy. The sheet resistance of the two-dimensional electron gas in the AlGaAs/GaAs system was distributed within ±1% on one wafer and ±1.5% among seven wafers. The standard deviation of the threshold voltage (the gate pinch-off voltage) for fabricated HIFETs (so-called HEMTs) was 9.7 mV in a 16 mm × 16 mm square, which represents the VLSI-level uniformity. The average noise figure of 0.5 μm gate HIFETs at 12 GHz was 0.96 dB with a 0.06 dB standard deviation.

An AlN/GaN insulated gate heterostructure field effect transistor with regrown n+GaN source and drain contact

A nobel insulated gate heterostructure field effect transistor (IG-HFET) was demonstrated. The layer structure under the gate consisted of a thick AIGaN barrier. an n + GaN channel 15 nm thick, and an AIN insulator 4 nm thick, grown sequentially by MOCVD. The device operated with gate voltage up to + 3 V. The pinch-off voltage was about 0 V, which resulted from the very high Schottky barrier height and the very thin AIN layer. The measured transconductance g m was 235 mS/mm for L g = 1.4 μm, which is the highest so far reported.

Se and Te doping in LP-MOCVD-grown GaSb using H2Se and DETe

Abstract Se and Te doping in GaSb grown by LP-MOCVD have been studied using SIMS and the Van der Pauw technique. The concentrations of Se atoms were varied from 8X1016 to 1.4X1020 cm-3 by varying [H2Se]. The relation was linear up to 1X1018 cm-3; above this, the Se atoms were incorporated superlinearly with [H2Se]. At this transition and where the V/III reactant ratio decreased, Se incorporation was enhanced by one order of magnitude. This behavior suggests the formation of complexes between Ga and Se on the growing surface. The carrier density was by a factor of 2 below the Se atom density before the transition. The carrier density had a maximum of 4X1017 cm-3, above which point it dropped rapidly. Temperature-dependent Hall data showed that the shallow donor density decreased with the formation of a deep donor, which explained the decrease in carrier density at room temperature. It is not yet clear whether the deep donor formation is related to the complexes. Similar doping behavior has been observed for Te doping.

InAs-GaSb hot electron transistors grown by metalorganic chemical vapor deposition

Abstract We report on GaSb and GaInSb epilayers grown on GaSb substrates by LPMOCVD. Growth was performed at 100 Torr from TMGa, TMIn, and TMSb. The growth rate using TMGa is reduced at lower temperatures. This determines x in Ga 1− x In x Sb. The growth efficiency is also reduced by adding TMSb to the vapor. A hot-electron transistor structure was also grown. The device uses a GaSb emitter barrier and 100Awide InAs base. A GaSb collector barrier and a Ga 0.9 In 0.1 Sb(200A)/GaSb collector barrier were used. The latter device exhibits a common-emitter current gain in excess of 1 at room temperature.