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This article investigates steady-state nonequilibrium conditions in metal–oxide–semiconductor (MOS) capacitors. Steady-state nonequilibrium conditions are of significant interest due to the advent of wide-gap semiconductors in the arena of MOS (or metal–insulator–semiconductor) devices and due to the scaling of oxide thickness in Si technology. Two major classes of steady-state nonequilibrium conditions were studied both experimentally and theoretically: (i) steady-state deep depletion and (ii) steady-state low level optical generation. It is found that the identification and subsequent understanding of steady-state nonequilibrium conditions is of significant importance for correct interpretation of electrical measurements such as capacitance–voltage and conductance–voltage measurements. Basic implications of steady-state nonequilibrium conditions were derived for both MOS capacitors with low interfaces state density Dit and for oxide semiconductor interfaces with a pinned Fermi level. Further, a photoluminescence power spectroscopy technique is investigated as a complementary tool for direct-gap semiconductors to study Dit and to monitor the interface quality during device fabrication.

The activation efficiencies of implanted Si, Be, and C in GaAs0.93P0.07 have been measured in the annealing range 650–950 °C. Be provides much higher sheet hole densities than C, even when the latter is coimplanted with Ar to enhance the electrical activity. The maximum activation efficiency of Be is ∼60% at a dose of 5×1014 cm2 whereas that of C is an order of magnitude lower. Si produces donor activation percentages up to ∼20% under optimized annealing conditions. Capless proximity annealing is adequate for surface preservation up to ∼950 °C, as measured by scanning electron microscopy and atomic force microscopy. Photoluminescence measurements provide evidence that nonradiative, damage‐related point defects remain in the GaAsP even after annealing of 950 °C.

Properties of Ga2O3 thin films deposited by electron‐beam evaporation from a high‐purity single‐crystal Gd3Ga5O12 source are reported. As‐deposited Ga2O3 films are amorphous, stoichiometric, and homogeneous. Excellent uniformity in thickness and refractive index was obtained over a 2 in. wafer. The films maintain their integrity during annealing up to 800 and 1200 °C on GaAs and Si substrates, respectively. Optical properties including refractive index (n=1.84–1.88 at 980 nm wavelength) and band gap (4.4 eV) are close or identical, respectively, to Ga2O3 bulk properties. Reflectivities as low as 10−5 for Ga2O3/GaAs structures and a small absorption coefficient (≊100 cm−1 at 980 nm) were measured. Dielectric properties include a static dielectric constant between 9.9 and 10.2, which is identical to bulk Ga2O3, and electric breakdown fields up to 3.6 MV/cm. The Ga2O3/GaAs interface demonstrated a significantly higher photoluminescence intensity and thus a lower surface recombination velocity as compared to ...

We study the nonlinear properties of bulk AlGaAs and GaAs/AlGaAs multiple quantum wells(MQW) below the half‐band‐gap energy using subpicosecond pulses between 1.65 and 1.7 μm. In the bulk material we find a value for the nonlinear index n 2 = +3.6× 10−14 cm2/W and a two‐photon absorption coefficient β = 0.26 × 10−4 cm/MW. In the MQW we measure an n 2 up to 2.4 times larger, and we attribute this enhancement to a stronger 1S‐exciton intermediate state. The β value is up to 25 times larger in the MQW. This larger value may result from midgap states that resonantly enhance the virtual intermediate state in two‐photon absorption and act as a real transition in a two‐step absorption process. The resulting figure of merit (2n 2/βλ) for the bulk (MQW)material is 17 (1.6), which means that these semiconductors below half band gap are appropriate for all‐optical switching and quantum optics applications. We confirm that n 2 is instantaneous on the 300 fs time scale of our pulses from self‐phase‐modulation spectra as well as time‐resolved pump‐probe measurements. However, we find an intriguing exchange of energy between the two orthogonal axes as evidenced by the signal along the probe axis following the negative derivative of the pump intensity. This result may be explained by self‐phase modulation of the pump combined with a low‐frequency Raman process that couples the modes along orthogonal axes.

We present a detailed theoretical study on the optical and L–I characteristics of implant-apertured index-guided vertical-cavity surface-emitting lasers. Our theory is based on a beam propagation method combined with thermal, gain, and rate-equation models. Spatial hole burning and modal competition are taken into account. Our results are in excellent agreement with the experimental data and show the effect of the current aperture size (determined by the ion implant) on the modal performance of these devices. In particular, the current-aperture size can be fixed independently from the index-guide size to obtain minimum threshold, single-mode operation.

We show that two-photon photocurrent imaging can be used to nondestructively study vertical cavity surface emitting lasers on a microscopic level. In particular, we study the aperture isolation created by shallow ion implantation. The combination of two-photon backside imaging and a probe station is ideal for internal and full wafer characterization. The required peak and average power levels for testing can be easily satisfied by available compact ultrafast laser sources, making the technique practical and user friendly.

Using metal organic chemical vapor deposition, we have fabricated self-organized quantum dots that emit efficiently at 1.3 μm at room temperature. They are grown on GaAs and consist of InAs covered with an InGaAs cap layer. Their density is 2×1010 cm−2 as determined by transmission electron microscopy. Room-temperature photoluminescence shows a 36 meV broad line at 1.3 μm, corresponding to the quantum-dot ground state, with excellent uniformity across the wafer. The efficiency of this emission is reduced only by a factor of 4 with respect to low temperature showing the high quality of the sample.

We have fabricated high power carbon‐doped InGaAs/AlGaAs lasers using an impurity‐induced layer disordering process to define the active region. The advantage of carbon doping is that it exhibits significantly lower diffusivity compared to other p‐type dopants, thereby avoiding displacement of the p‐n junction, even at the high temperatures and long diffusion times required by the disordering process. Secondary ion mass spectrometry (SIMS) measurements before and after Si diffusion show the p‐n junction position to be unchanged during processing. The carbon was introduced using CCl4 as an extrinsic precursor, giving improved control over doping levels and ternary growth conditions that is not available with intrinsic carbon doping. Thresholds of 20 mA and slope efficiencies of 0.44 mW/mA at 25 °C were obtained for lasers with cavity lengths of 500 μm and coated facets.

The carbon doping properties of GaAs grown by low pressure (30 Torr) organometallic vapor phase epitaxy at 520–700 °C with CCl4 as the dopant precursor were compared for the four possible combinations of trimethylgallium (TMGa), triethylgallium (TEGa), arsine (AsH3), and tertiarybutylarsine (TBAs). Secondary ion mass spectrometry (SIMS), Hall measurements, and infrared absorption were used to characterize the GaAs:C layers. Very high C‐doping concentrations (∼1020 cm−3) could be obtained using either TMGa or TEGa and AsH3. The use of TBAs instead of AsH3 led to a significant reduction in carbon incorporation, by approximately a factor of 5–10 per mole of As precursor over the growth temperature range examined. Hydrogen at significant concentrations (1–6×1019 cm−3) was detected by SIMS in GaAs: C layers grown at ≤550 °C utilizing all four combinations of Ga/As precursors. The existence of electrically inactive C‐H complexes was confirmed by observation of the C‐H stretching mode at 2635 cm−1. A post‐growth...

High quality AlxGa1−xAs has been grown by low‐pressure (30 Torr) organometallic vapor phase epitaxy (OMVPE) using a novel precursor, trimethylamine alane (TMAAl), as the aluminum source. The epilayers exhibited featureless surface morphology, very strong room‐temperature photoluminescence (PL), and excellent compositional uniformity (x=0.235±0.002 over a 40 mm diameter). The residual carbon incorporation, which determined the background doping, depended largely upon the choice of gallium precursor. Using triethylgallium, carbon incorporation could be largely suppressed ([C]≪1016 cm−3). The carbon‐related emission intensity was less than the bound exciton emission in low‐temperature (1.6 K) PL even at excitation powers as low as 50 μW cm−2. By sharp contrast, the use of trimethylgallium led to much higher C concentrations (2–5×1017cm−3). Under appropriate conditions, therefore, the use of TMAAl produces extremely high purity AlGaAs of superior quality to AlGaAs grown using conventional precursors.

The addition of SF6 to CH4/H2 discharges is shown to produce a significant increase in the selectivity for dry etching of both InGaAs and InP over AlInAs. The selectivity is a strong function of the dc bias on the sample during the reactive ion etching, with equirate removal of InGaAs and AlInAs for biases above 300 V. For lower bias values, the etch stop mechanism is related to the formation of Al‐F and In‐F species on the AlInAs surface, as evidenced by x‐ray photoelectron spectroscopy. The use of SF6 allows independent variation of the ratio of F to the other reactive species, in comparison to the use of fixed ratio gases such as C2H4F2 or CH3F.

p-n junctions have been formed in lightly n-type (1017cm−3) bulk, single-crystal ZnO substrates by diffusion of P from a Cd3P2, arsenic and red phosphorous dopant source in a closed-ampoule system. The P incorporation depth was found to be ∼200nm after diffusion at 550°C for 30min, as determined by secondary ion mass spectrometry profiling. The resulting structures show rectification, with on-off current ratios of ∼70 at +3∕−5V. The forward current ideality factor was ⩾2, consistent with multiple current transport mechanisms present in the junction, such as defect-assisted tunneling and conventional carrier recombination in the space-charge region via midgap deep levels. The forward turn-on voltage, VF was ∼4V at 300K with a specific on-state resistance (RON) of ∼21mΩcm2. The activation energy of the forward current at low forward biases was ∼1.4eV. This is also consistent with carrier recombination in the space charge region via a midgap deep level.

The etch rate, surface morphology and atomic composition, and depth of hydrogen passivation of Si dopants in n‐type GaAs and AlGaAs have been examined as a function of the temperature of the sample during reactive ion etching in C2H6/H2. While there is no temperature dependence of the etch rate of AlGaAs over the range 50–350 °C, the etching of GaAs shows an increase of a factor of 2 between 150 and 250 °C, decreasing at higher temperatures. The As‐to‐Ga ratio in the near‐surface region of GaAs remains unchanged over the whole temperature range investigated and there is no polymer deposition. The etched surface morphology is smooth for both GaAs and AlGaAs for all temperatures while the depth of Si dopant passivation by hydrogen shows an increase with increasing substrate temperature during the etching treatment.