InGaAs films have been deposited on semi-insulating InxGa1−xAs (x=0.04–0.05) substrates with improved material properties compared to similar InGaAs films grown on GaAs substrates. For near lattice matched conditions the films grown on InGaAs substrates have a smooth surface morphology compared to a dislocation-induced cross hatch morphology on GaAs substrates. The resulting film double crystal x-ray linewidths are considerably narrower. The InGaAs film photoluminescence intensity is stronger with a narrower x-ray linewidth due to the elimination of lattice mismatch dislocations. Also the Hall mobilities are higher for the films grown on InGaAs substrates.

Low temperature (LT) InAlAs buffer layers grown lattice matched to InP substrates using a combination of trimethylarsenic and arsine were demonstrated. The LT InAlAs buffer layer showed excellent surface morphology with a maximum resistivity of 2×105 Ω cm at a growth temperature of 475 °C. Low temperature photoluminescence and Hall-effect measurements confirming the high quality of epitaxial layers grown on top of the LT InAlAs buffer layer. Electrochemical capacitance voltage measurements consistently confirmed the absence of conductive impurity spikes at the epitaxial/substrate interface.

Atomic layer epitaxy (ALE) growth of InP was investigated using trimethylindium (TMI) and tertiarybutylphosphine (TBP) in a horizontal atmospheric reactor. The studied growth parameters were exposure times, TMI and TBP fluxes, and growth temperature. Self-limiting ALE growth of InP was achieved at a growth temperature of 340°C. Substantial increases in the TMI flux and higher growth temperatures exceeding 340°C resulted in growth rates exceeding 1 monolayer per cycle. Uniform ALE InP layers were verified by cross-sectional transmission electron micrography and sputtered Auger profiling. The application of thin ALE InP layers (15 Å) on GaAs surfaces was investigated using X-ray photoelectron spectroscopy, 77 K photoluminescence, and 300 K photoreflectance. The absence of arsenic oxide and an increase in the photoluminescence intensity by a factor of 2 were observed after InP passivation.

Inverted, pulse-doped AlGaAs/InGaAs pseudomorphic high electron mobility transistor structures were grown by molecular-beam epitaxy. Growth conditions were optimized to improve the quality of the selectively doped AlGaAs layer and to minimize dopant diffusion into the InGaAs channel. The sheet densities and mobilities of the inverted structure were found to be essentially equivalent to those obtained with the normal structure. Shubnikov–de Haas measurements exhibited strong oscillations in the magnetoresistance and plateaus in the Hall resistance. Four optical transitions from the lowest bound electron and hole quantum well states were observed in room-temperature photoluminescence spectra.

Si delta-doped In0.15Ga0.85As/GaAs strained quantum wells are demonstrated by atmospheric pressure metalorganic chemical vapor deposition. The samples were characterized by variable temperature Hall effect, high magnetic field magnetoresistance, quantum Hall effect, capacitance-voltage measurements (C-V), and secondary-ion mass spectroscopy. The C-V profile showed a full width at half maximum as narrow as 15 Å. Two-dimensional electron gas transport was verified by observing step-like structures in the quantum Hall effect in samples containing sheet densities less than 5×1012 cm−2. Sheet densities as high as 1.0×1013 cm−2 were achieved. C and O contamination were not observed during the Si delta-doping process.

A compositionally graded InGaP alloy layer grown on a Si-doped InP layer was used to enhance the Schottky barrier height of InP. The fabricated diodes were characterized by Auger depth profiling, variable temperature I-V, capacitance-voltage (C-V), and internal photoemission. Rectification behavior with a low leakage current was achieved (J=8.3×10−7 A/cm2 at −1V). An enhanced Schottky barrier height of 1.18 eV was measured. The large barrier height permitted a reliable C-V profile of a moderately doped InP layer (7×1017 cm−3).

Undoped and modulation doped InAlAs/InP heterostructures with excellent optical and electrical characteristics are demonstrated using tertiarybutylphosphine (TBP). Low-temperature photoluminescence spectra showed the presence of a type II interface transition indicating the high quality of the interface. Two-dimensional electron gas transport in a modulation doped sample containing a sheet density of 1.8×1012 cm−2 was verified by observing plateaus in the quantum Hall effect. These results confirmed that TBP can be substituted for phosphine for the growth of high quality InAlAs/InP heterostructures.

Pulse-doped pseudomorphic AlGaAs/InGaAs high electron mobility transistors with two InGaAs channels have been grown by molecular-beam epitaxy. Electrical measurements indicate that the two channels are contributing nearly equally to the conduction. The sheet density is approximately twice that of the single channel structure, and good electron mobilities are obtained. Shubnikov–de Haas measurements confirm the two dimensional transport in the structure. Direct current measurements on device structures exhibit a double peak in the transconductance, low source resistance, and a sharp pinch-off characteristic.

We have confirmed the presence of a two-dimensional electron gas (2DEG) in a wide band-gap GaN-AlxGa1−xN heterojunction by observing steplike features in the quantum Hall effect. The 2DEG mobility for a GaN-Al0.13Ga0.87N heterojunction was measured to be 834 cm2/V s at room temperature. It monotonically increased and saturated at a value of 2626 cm2/V s at 77 K. The 2DEG mobility remained nearly constant for temperatures ranging from 77 to 4.2 K. Using Shubnikov–de Haas (SdH) measurements the two-dimensional carrier concentration was estimated to be 1×1011 cm−2. The peak mobility for the 2DEG was found to decrease with the heterojunction aluminum compositions in excess of 13%.

Photoreflectance (PR) and reflectance have been applied to characterize undoped and modulation-doped heterostructures of AlGaAs/GaAs grown by metal-organic chemical vapor deposition. The PR spectra were taken on these samples after sequential etching steps in a phosphoric acid etch to study the effects of the surface electric field, the heterointerface, and the two-dimensional electron gas. PR spectra were also taken with an external electric field applied through a transparent gate electrode. The results show that the oscillations appearing near the bandgap energy of GaAs are Franz–Keldysh oscillations originating from the large surface electric field. The surface electric field of the heterostructures can be modified through the application of an external electric field or by etching. The oscillation period is observed to increase with increasing reverse bias or with etching of the GaAs cap layer and the PR features disappear at a forward bias of 0.45 V. The very sharp features associated with the GaAs bandgap energy after etching have also been verified to be Franz–Keldysh oscillations and the presence of a two-dimensional electron gas cannot be confirmed with PR.

Si delta-doped GaAs field-effect transistors (FETs) are demonstrated by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) and characterized by Hall-effect, capacitance-voltage (C-V), and Shubnikov de-Haas measurements. The Si delta doping was accomplished by interrupting the growth and flowing silane with controlled timing under an arsenic overpressure. Devices with 0.5 μm gate length (Ns=2.2×1012 cm−2) were fabricated with a maximum extrinsic transconductance of 140 mS/mm and a current gain cutoff frequency of 17 GHz. The transconductance as a function of gate voltage showed a plateau region through a range of 1.5 V further supporting spatial confinement of the electrons.

Inverted pseudomorphic high electron mobility transistor (HEMT) and inverted HEMT heterostructures are demonstrated by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) for the first time and characterized by transmission electron microscopy (TEM), variable temperature Hall effect, and Shubnikov–de Haas measurements. TEM micrographs of both structures show distinct and sharp heterojunction interfaces without indications of interface roughness at the AlGaAs/channel layer interface. Variable temperature Hall effect measurements reveal a monotonic increase in mobility as the temperature is lowered. For the inverted HEMT, the mobility at 15 K is 90 000 cm2/V s with a sheet density of 8.2×1011 cm−2. The mobility of the inverted pseudomorphic HEMT at 15 K is 73 000 cm2/V s with a sheet density of 1.5×1012 cm−2. Shubnikov–de Haas measurements at 4.2 K in magnetic fields up to 18.5 T show clear magnetoresistance oscillations and plateaus in the quantum Hall effect confirming the existence of a two-dimensional electron gas. Fast Fourier power transform of the magnetoresistance versus magnetic field shows two subband levels with a total sheet density of 8.7×1011 cm−2 for the inverted HEMT and a total sheet density of 1.55×1012 cm−2 for the inverted pseudomorphic HEMT in close agreement to the variable temperature Hall effect measurement results.