This work describes using metal-organic chemical vapor deposition (MOCVD) to directly deposit III-V materials on Si/Ge-based substrates, with the primary focus being the methodology used to develop a manufacturable heterointegration process.

In this letter, we report the first demonstration of InGaP/GaAs heterojunction bipolar transistors (HBTs) on germanium-on-insulator (GOI) substrates. We have performed physical characterization of the epitaxial layers to verify the high quality of the III-V epitaxial material grown on the GOI substrates and performed dc characterization of large-area InGaP/GaAs HBTs fabricated on the substrates. The InGaP/GaAs HBTs realized on GOI substrates were compared with identical devices grown on bulk germanium substrates and similar devices on semi-insulating GaAs substrates.

To meet the requirement for today’s 2.4GHz high power circuit applications, we designed and processed high power heterojunction bipolar transistors (HBTs) . The InGaP/GaAs HBTs with current gain 52.2, BVCEO=16.1V, BVBCO=24.6V, ft=39GHz and fmax=139GHz were archieved from a 3x10µ µm 2 emitter contact. The performance meets the specifications required.

Photoluminescence (PL) above the excitation energy is observed in a single GaAs-InGaP quantum well (QW) and heterostructure as well as in a InP-GaAs superlattice (SL) and in strained layers. It is shown that sub-gap excitation (1.468 eV) of n-type delta-doped GaAs/GaInP quantum structure leads to an up-converted hot carrier PL emission with energy gains as high as 450 meV. The up-conversion energy in GaAs-InGaP heterostructures is 50 meV which is originated from the GaAs layer. In InP-GaAs SL, the sub-gap excitation results in a hot PL at 1.55 eV. It is also shown that the sub-gap excitation can be used to confirm the changes in band energies of a strained layer.

This work describes the temperature dependence of the DC and small-signal performance of InGaP/GaAs heterojunction bipolar transistors (HBT's) with different collector thicknesses. Detailed analyses of the small-signal performance and the temperature dependence of both DC and high-frequency parameters are presented. An HBT delay-time analysis is also presented and justified empirically. In addition, the factors causing the decrease in f/sub T/ with temperature are described, and the variations in collector resistance and collector drift velocity with temperature are determined.

InGaP/GaAs heterojunction bipolar transistors (HBTs) with an f(t) = 126 GHz and a beta = 162 have been demonstrated, and to the best of our knowledge this is the highest reported f(t) for an InGaP/GaAs HBT not employing a ballistic collection transistor design. The excellent dc and high frequency characteristics were achieved using a 300 Angstrom thick graded base and a 2000 Angstrom thick collector. These data show that InGaP/GaAs HBTs can simultaneously achieve both excellent dc and high frequency characteristics and that InGaP/GaAs HBTs are potentially useful in many high-speed circuit applications.

The effect of high temperature annealing on the formation of carbon precipitates in the base region of InGaP/GaAs heterojunction bipolar transistors (HBTs). This work for the first time, shows that after annealing at only 600degreesC, a sample doped at 5.5x10(19) cm(-3) displays carbon precipitation. InGaP/GaAs HBT structures were grown for the annealing study. The annealing process not only removes hydrogen from the base but also creates carbon precipitates. DC current gain measurements imply that the carbon precipitates increase base recombination. These results are very important in the growth and post growth growth annealing of high gain HBTs.

Resulting from excellent direct-current, high-frequency, and reliability characteristics, HBT technology has attracted much attention in recent years. To help technology development groups determine if HBTs are the correct solution for 100 GHz applications, this work briefly describes the progress of HBT technology during the last decade and sets forth some of the reasons for employing this technology. Different HBT technologies are discussed and the current state-of-the-art is presented. Finally the existing limitations and future of HBT technology are discussed.

Recently InGaP/GaAs HBTs have demonstrated performance comparable to AlGaAs/GaAs and have proven to be well suited for high-speed and low-noise applications. Despite the excellent performance of InGaP/GaAs HBTs, continued efforts towards reducing the delay associated with the emitter resistance and capacitance are required. To help minimize the emitter resistance, PdGe contacts on n-type GaAs were studied. This experiment studies the behavior of the PdGe alloyed on a hot plate for times less than 30 minutes and compares results to RTA alloys. Also studied is the behavior of the PdGe contacts alloyed in various ambients. Finally, the issues associated with performing a self-aligned emitter etch with PdGe contacts are also discussed.

A high concentration of hydrogen in the alloy ambient slows the formation of PdGe contacts and increases the resistance of the PdGe to GaAs etchants. The effects of alloy ambient on alloy formation, specific contact resistance, and chemical reactivity of PdGe contacts on n-type GaAs have been studied. A very low specific contact resistance of <1×10−7 Ω cm2 has been achieved on GaAs with PdGe contacts alloyed at 300 °C for 15 min in a hydrogen ambient. These results indicate that PdGe may be a desirable contact for GaAs-based transistors.

High-resistivity unintentionally-doped In0.49Ga0.51P lattice matched to GaAs has been grown via low-pressure metalorganic chemical vapor deposition at a reduced growth temperature. These layers have excellent surface quality and are single crystal. The resistivity increases exponentially as the growth temperature is decreased from 550 to 490 °C, resulting in a resistivity of ∼109 Ω cm for samples grown at 490 °C. In addition, the photoluminescence intensity decreases exponentially for growth temperatures below 550 °C, indicating an increase in nonradiative recombination related to an increasing trap concentration. For samples grown at 550 °C, constant capacitance deep level transient spectroscopy measurements show a strong broad peak at ∼200 °K with an ionization energy of 0.40±0.04 eV, verifying the presence of an electron trap. The gummel plot and I–V characteristics of an InGaP/GaAs heterojunction bipolar transistor (HBT) with a 2000-Å-thick InGaP buffer layer grown at 500 °C are identical to that of an HBT grown without the InGaP buffer layer, indicating that the semi-insulating InGaP layer is compatible with GaAs-based device epitaxy.

The effects of rapid thermal annealing on InP/InGaAs heterojunction bipolar transistors with a carbon-doped base have been studied. The hydrogen concentration in the base has been studied as a function of the anneal temperature and time. A 10 minute anneal at 590 degrees C under N-2 completely eliminates hydrogen from the base. By using shorter anneals and/or lower temperatures, the de and rf device performance were studied as a function of the base hydrogen concentration. The results show that the base sheet resistance decreases with annealing time as does the de current gain. As expected, the maximum frequency of oscillation increases as the base resistance decreases. The unity current-gain cutoff frequency, however, is significantly enhanced by removing hydrogen despite the resulting increase in the base hole concentration. A likely explanation for this behavior is that a large percentage of the hydrogen in the InGaAs base region incorporates as a compensating donor rather than forming a neutral CH complex.

To improve electrical isolation and simplify the heterojunction bipolar transistor (HBT) fabrication process, a semi-insulating InGaP buffer layer has been employed in an InGaP/GaAs HBT, Data is presented that demonstrates this buffer layer serves as an excellent isolation material, In addition, high-frequency HBT's have been fabricated and characterized to show that the buffer layer does not degrade device performance.

In this paper we report on the performance of InGaP/GaAs HETs with different compositionally graded InxCa1-xAs base regions. In previous work we have shown that a large built-in base field of similar to 8.6 kV/cm significantly improved the HBT current gain and unity current gain cutoff frequency. To further characterize the base transport in these HBTs, the magnitude of the E-field in the base and its contribution to electron transport have been studied. HBTs with the base graded linearly from GaAs at the emitter-base junction to InxGa1-xAs at the base-collector junction were fabricated and tested. As the base field was increased, the dc current gain increased by nearly 75% and the unity gain cutoff frequency increased by over 20% compared to a device with a standard non-graded base design. The saturation of the current gain and the base transit time at higher fields indicate that velocity-field characteristics play a significant role in base transport.

We studied the effect of group V switching times on the formation of interfacial layers in InGaP/GaAs heterostructures grown by LP-MOCVD using low temperature photoluminescence (PL), double crystal x-ray diffraction (DCXRD) and high resolution transmission electron microscopy (HR-TEM). Due to the severe substitution process of P by As, the quality of InGaP-to-GaAs interface was very sensitive to switching times. By optimizing the switching conditions, we were able to minimize the interfacial layers to one monolayer (ML) of In(0.5)G(0.5)As at the GaAs-to-InGaP interface and 1 ML of In0.65Ga0.35P0.15As0.85 at the InGaP-to-GaAs interface. Heterojunction bipolar transistors (HBTs) grown using this switching scheme showed excellent etch selectivity as well as de characteristics.