Heavily doped base GaInP/GaAs heterojunction bipolar transistor grown by chemical beam epitaxy

The first demonstration of a GaInP/GaAs heterojunction bipolar transistor grown by chemical beam epitaxy is reported. A common-emitter current gain of 30 at a current density of 110 A/cm/sup 2/ is obtained for a beryllium base doping as high as 8*10/sup 19/ cm/sup -3/. The base sheet resistance of 140 Omega / Square Operator is among the lowest reported values.<>     

A high-gain GaAs/AlGaAs n-p-n heterojunction bipolar transistor on(100) Si grown by molecular beam epitaxy

High-gain GaAs/AlGaAs n-p-n heterojunction bipolar transistors (HBT's) on Si substrates grown by molecular beam epitaxy (MBE) have been fabricated and tested. In this structure, an n⁺-InAs emitter cap layer was grown in order to achieve a nonalloyed ohmic contact. Typical devices with an emitter dimension of 50×50 μm² exhibited a current gain as high as 45 at a collector current density of 2×10³ A/cm² with an ideality factor of 1.4. This is the highest current gain reported for HBT's grown on Si substrates. Breakdown voltages as high as 10 and 15 V were observed for the emitter-base and collector-base junctions respectively. The investigation on devices with varying emitter dimensions demonstrates that much higher current gains can be expected     

Heterojunction bipolar transistors with SiGe base grown bymolecular beam epitaxy

High-quality SiGe heterojunction bipolar transistors (HBTs) have been fabricated using material grown by molecular beam epitaxy (MBE). The height of parasitic barriers in the conduction band varied over the wafer, and the influence of these barriers on controller current, early voltage, and cutoff frequency were studied by experiments and simulations. Temperature-dependent measurements were performed to study the influence of the barriers on the effective bandgap narrowing in the base and to obtain an expression for the collector-current enhancement. From temperature-dependent measurements, the authors demonstrate that the collector-current enhancement of the HBTs can be described by a single exponential function with a temperature-independent prefactor     

High-speed GaAs heterojunction bipolar phototransistor grown by molecular beam epitaxy

A novel heterojunction phototransistor (HPT) structure is proposed using two base regions such that the emitter-base depletion region is located in the wide-gap material. Very small area HPTs have been fabricated on semi-insulating substrates. Maximum current gain is ? = 300. The response time, with rise time as short as 250 ps and FWHM = 320 ps, has been obtained using a picosecond pulse dye laser.     

Double-heterojunction GaAlInAs/GaInAs bipolar transistor grown by molecular beam epitaxy

The first double-heterojunction In53Ga28Al19As/In53Ga47As bipolar transistors grown by molecular beam epitaxy on semi-insulating substrates were fabricated and characterized. We present a comparison between three types of structures: ones with two abrupt heterojunctions; ones with a thin small bandgap n-type layer (spacer) at the collector junction; and ones with two spacers. The use of the small bandgap spacer permits an increase in the collector efficiency while decreasing the recombination current in the emitter-base junction. The best devices of the third type (two spacers) exhibit a current gain up to 200 and an offset voltage of only 70 mV.     

InGaAs/lnP heterojunction bipolar transistor grown by all-solidsource molecular beam epitaxy

State-of-the-art InGaAs/InP heterojunction bipolar transistors were grown by all-solid source molecular beam epitaxy. Fabricated transistors showed cutoff frequencies of >100 GHz with an emitter area of 1.5×5 μm². Together with recent studies. These results demonstrate that the valved cracker technique is a very competitive nontoxic growth method     

Induced base transistor fabricated by molecular beam epitaxy

A novel three-terminal hot-electron device, the induced base transistor (IBT), has been fabricated by molecular beam epitaxy (MBE). Two-dimensional electron gas (2-DEG) induced by the applied collector field in an undoped GaAs quantum well is used as the base of the IBT. The common-base current gain α has been achieved as high as 0.96 under a collector bias of 2.5 V and an emitter current of 3 mA.     

AlGaAs/GaAs pnp heterojunction bipolar transistor with carbon-doped collector and emitter grown by atomic layer epitaxy

The first AlGaAs/GaAs pnp heterojunction bipolar transistor (HBT) grown entirely by atomic layer epitaxy (ALE) is reported. Carbon was used as the p-type dopant in the emitter and collector. The use of carbon, with its low diffusivity and the potential for very heavy doping, will lead to reduced emitter and collector resistances in a pnp structure. For the devices reported here, a common emitter current gain over 100 was obtained, with good I/V characteristics.<>     

An uncompensated silicon bipolar junction transistor fabricated using molecular beam epitaxy

The first silicon bipolar junction transistor fabricated using molecular beam epitaxy is reported. Epitaxial layers defining the collector, base, and emitter regions are grown successively at 850°C. Because no thermal diffusion steps are involved, junction location and base width are precisely defined. The final structure is mesa isolated using reactive ion etching. A peak forward current gain of 60 is measured. This technique is expected to be applicable to the development of very narrow base, ultrahigh speed bipolar transistors.     

Very high purity In0.53Ga0.47As grown by molecular beam epitaxy

Very high purity In0_0.53Ga_0.47As layers were grown by molecular beam epitaxy (MBE). Origins ofn-type impurities in undoped In_0.53Ga_0.47As grown on an InP:Fe substrate were systematically examined. The most possible origins were impurities diffusing from the InP:Fe substrate and those contained in As molecular beam. These impurities were dramatically reduced by using an InAlAs buffer layer and a growth condition of high substrate temperature and low As pressure. The lowest electron concentration of the In0_0.53Ga_0.47As layer wasn = 1.8 × 10¹³ cm_-3 with mobilitiesμ = 15200 cm²/Vs at 300 K andμ = 104000 cm²/Vs at 77 K.     

An (Al,Ga)As/GaAs heterostructure bipolar transistor with nonalloyed graded-gap ohmic contacts to the base and emitter

Graded regions of n-(Ga,In)As and p-Ga(As,Sb) were incorporated side-by-side as emitter and base contacts, respectively, into an n-p-n (Al,Ga)As/GaAs heterostructure bipolar transistor (HBT). The process involved two separate molecular beam epitaxy (MBE) growths, leading to base contact regions that were self-aligned to the emitter mesas. The devices could be easily probed with pressure contacts even prior to any metallization, and excellent characteristics were obtained after final metallization. Contact resistivities of 5 × 10^-7and 3 × 10^-6Ω.cm²were measured for n- and p-type graded-gap ohmic contact structures, respectively.     

Enhancement of Si-donor incorporation by Ga adatoms in Si delta-doped GaAs grown by molecular beam epitaxy

We report on the realization of a modified delta doping technique to obtain doping profiles in MBE grown GaAs, measured by capacitance-voltage (C-V) methods with full-widths at half-maximum (FWHM)s of 25 ± 5Å and peak concentrations of up to 1.1 × 10¹⁹ cm^?3. In this modified delta doping technique, both the Ga and Si shutters were opened for 15 sec during the delta doped layer growth while only the Si shutter is opened during conventional delta doping. Comparison of the two techniques under the same dopant flux and shutter-open-time interval shows that higher sheet-carrier concentrations with narrower FWHMs and higher peak concentrations are obtained with the modified delta doping than with the conventional delta doping method. This suggests that Si donor incorporation is enhanced by the Ga adatoms while broadening of the Si donor distribution is still negligible for this short time interval. The effects of the substrate temperature and the shutter-open time on the Si donor distribution have also been investigated.     

High resistivity LT-In0.47Ga0.53P grown by gas source molecular beam epitaxy

Low-temperature (LT) growth of In_0.47Ga_0.53P was carried out in the temperature range from 200 to 260°C by gas source molecular beam epitaxy using solid Ga and In and precracked PH₃. The Hall measurements of the as-grown film showed a resistivity of ∼10⁶ Ω-cm at room temperature whereas the annealed film (at 600°C for 1 h) had at least three orders of magnitude higher resistivity. The Hall measurements, also, indicated activation energies of ∼0.5 and 0.8 eV for the asgrown and annealed samples, respectively. Double-crystal x-ray diffraction showed that the LT-InGaP films had ∼47% In composition. The angular separation, Δθ, between the GaAs substrate and the as-grown LT-InGaP film on (004) reflection was increased by 20 arc-s after annealing. In order to better understand the annealing effect, a LT-InGaP film was grown on an InGaP film grown at 480°C. While annealing did not have any effect on the HT-InGaP peak position, the LT-InGaP peak was shifted toward the HT-InGaP peak, indicating a decrease in the LT-InGaP lattice parameter. Cross-sectional transmission electron microscopy indicates the presence of phase separation in LT-InGaP films, manifested in the form of a “precipitate-like” microstructure. The analytical scanning transmission electron microscopy analysis of the LT-InGaP film revealed a group-V nonstoichiometric deviation of ∼0.5 at.% P. To our knowledge, this is the first report about the growth and characterization of LT-InGaP films.     

Structural properties of GaAsN grown on (001) GaAs by metalorganic molecular beam epitaxy

Detailed transmission electron microscopy (TEM) and transmission electron diffraction (TED) examination has been made of metalorganic molecular beam epitaxial GaAsN layers grown on (001) GaAs substrates. TEM results show that lateral composition modulation occurs in the GaAs_1−xN_x layer (x 6.75%). It is shown that increasing N composition and Se (dopant) concentration leads to poor crystallinity. It is also shown that the addition of Se increases N composition. Atomic force microscopy (AFM) results show that the surfaces of the samples experience a morphological change from faceting to islanding, as the N composition and Se concentration increase. Based on the TEM and AFM results, a simple model is given to explain the formation of the lateral composition modulation.     

Selenium doped high-index GaAs epilayers grown by molecular beam epitaxy

Using elementary Se we grew Se-doped GaAs films on GaAs (111), (411), (711) and (100) substrates by molecular beam epitaxy. The films grown on all the high-index substrates showed n-type conduction and the maximum carrier concentration reached 2.1 × 10¹⁹ cm⁻³ for the film grown on the (411)B substrate. The carrier concentration began to saturate at a Se concentration near 10¹⁹ cm⁻³ but continued to increase up to a Se concentration of 2 × 10²⁰ cm⁻³. Above 2 × 10²⁰ cm⁻³ Se concentration, slow reduction of the carrier concentration was observed. We obtained excellent surface morphology when n-type GaAs films were grown on (411)A and (711)B substrates even at a Se concentration of 7 × 10²⁰ cm⁻³.     

Investigation of high In content InGaAs quantum wells grown on GaAs by molecular beam epitaxy

Excitonic resonances and the quantum confined Stark effect are observed near 1.3 mu m in InGaAs quantum wells grown on GaAs using a slowly graded InGaAs buffer. The pin structure performs as a modulator with a relative transmission modulation of 12% at 1.3 mu m and as a low leakage photodetector.<>     

Antiphase boundary of GaAs films grown on Si(001) substrates by molecular beam epitaxy

Single and double domain GaAs film growth on double domain Si(001) substrates by molecular beam epitaxy were observed. The domain structure of the film did not succeed to the domain structure of the substrate surface but was decided by a direction of slight misorientation of the substrate. To explain this, it has been proposed that the antiphase boundary (APB) of the film is dominantly non-stoichiometric,i.e., the APB is composed of the same polar {11n} or {nn1} (n = 1, 2, ….) planes of the adjacent domains. Growth simulation based on this model about the APB has explained well the experimental results that a double domain film can grow on a Si(001) surface which is exactly oriented or is misoriented towards a 〈100〉 direction.     

Vertical integration of an In/sub 0.15/Ga/sub 0.85/As modulation-doped field effect transistor and GaAs laser grown by molecular beam epitaxy

A vertically integrated structure consisting of an In/sub 0.15/Ga/sub 0.85/As pseudomorphic modulation doped field effect transistor (MODFET) and a GaAs graded index separate confinement heterostructure single quantum well (GRINSCH SQW) laser was grown by molecular beam epitaxy. Wafers containing integrated MODFET/laser layers produced MODFETs with DC and microwave performance comparable to wafers containing only MODFET layers, indicating that the modulation doping and the strained In/sub 0.15/Ga/sub 0.85/As channel were largely unaffected by the long, high temperature laser growth. The lasers had threshold currents similar to identical structures grown on n-type substrates and the integrated structures had a -3dB modulation bandwidth of 3.5 GHz.<>     

Very high electron mobility In0.8Ga0.2As heterostructure grown by molecular beam epitaxy

A very high electron mobility pseudomorphic In_0.8Ga_0.2As heterostructure is successfully grown on InP both by the elimination of the overshoot of flux densities and by the precise control of the flux ratio through a new calibration technique of RHEED oscillations in an MBE system. The critical layer thickness for the pseudomorphic growth of InGaAs on InP is found to follow the energy balance model, and a very high 2DEG mobility of over 1.5 and 16 m²/Vs at 293 and 10 K, respectively, is obtained.