G. O. Munns

The optimization of InxGa1-xAs and InP growth conditions by CBE

Abstract Minimization of the number of experiments needed to fully characterize and optimize the growth of epitaxial material is the first important step in realizing state of the art device structures. While widely used in some fields such as chemical engineering, response surface modeling (RSM) has been little used in crystal growth applications. Using RSM, input parameters such as substrate temperature hydride injector temperature and V III ratio, were simultaneously adjusted to characterize the crystal growth process. This technique identified interactions among parameters, minimized the number of experiments necessary to understand and optimize the process, and minimized the variability of the growth process. RSM has been applied to the CBE growth of InGaAs and InP with the purpose of generating an operating point at which both good surface morphology and high mobility material can be produced. Although the best 77 K InP mobility was 70,000 cm 2 /V⋯s, in order to improve the surface quality the input parameters were changed so that the final mobility was 37,000 cm 2 /V⋯s. Although the quality of the InGaAs layers showed a dependence on the reactor history, there did not appear to be any sensitivity to variations made in the operating conditions. The best 77 K InGaAs mobility was 62,500 cm 2 /V⋯s.

The potential of InP IMPATT diodes as high-power millimeter-wave sources: First experimental results

Extensive simulations of GaAs and InP transit-time diodes clearly show the advantages of the InP material system. RF power levels of more than 1 W as well as dc-to-RF conversion efficiencies of more than 18% around 100 GHz can be expected from optimized diodes. The fabrication process was adopted from the process for InP Gunn devices on integral heat sinks. Typical RF power levels were around 80 mW from about 60 GHz to 80 GHz with corresponding dc-to-RF conversion efficiencies ranging from 3% to 4%. The best device yielded more than 110 mW (more than 5%) at 64.7 GHz, 82 mW (3.7%) at 79 GHz and 55 mW (2.4%) at 84.8 GHz. These preliminary experimental results are better than those of single-drift flat-profile GaAs IMPATT diodes on integral heat sinks and also indicate the strong potential for millimeter-wave InP IMPATT diodes.

Investigation and optimization of InGaAs/InP heterointerfaces grown by chemical beam epitaxy using spectroscopic ellipsometry and photoluminescence

Spectroscopic ellipsometry (SE) has been used to investigate transition layers for InGaAs/InP heterointerfaces. For the case of InGaAs on InP, we have found that the samples can be best modeled by a strained InxGa1-xAs film with the possible presence of a thin interface region (15Å). We are unable to conclusively determine the existence of such a thin transition region. For InP on InGaAs, we find clear indications of As contamination in the bulk film, and that the addition of a thin interface region of In0.75Gao0.25As0.5P0.5 improves both the numerical fit and shape of the dielectric response curves, especially around E1 and E1+ Δ1 where the effects of a transition region are most pronounced. However, difficulties in modeling the dielectric response of the contaminated InP film make identification of an interface transition region only speculative at this point. Multiple single quantum well structures have also been grown and analyzed with 7K photoluminescence. The quality of the quantum wells shows strong dependence on the gas switching sequence used at the heterointerfaces. The best switching sequence produced a 0.5 nm well with a 7K FWHM of only 12.3 meV. Multiple quantum wells have also been grown to investigate the uniformity and repeatability of our system. Twenty period MQWs with a well width of 1.6 nm display a 14K FWHM of 7.9 meV.

Theoretical and experimental studies of the effects of compressive and tensile strain on the performance of InP-InGaAs multiquantum-well lasers

The authors have studied, both theoretically and experimentally, the effects of biaxial strain upon the performance characteristics of broad-area InP-InGaAsP-In/sub x/Ga/sub 1-x/As (0.33 >

A fully integrated monolithic D-band oscillator-doubler chain using InP-based HEMTs

The experimental characteristics of a monolithic D-band oscillator-doubler chain are reported, together with the design, monolithic integrated circuit (MMIC) implementation, and testing. The circuits were fabricated using submicron (0.1- mu m) InAlAs/InGaAs high-electron-mobility transistors (HEMTs) and had on-chip bias stabilization circuitry and an integrated E-field probe for direct radiation into the waveguide. The oscillation signal was detected over a frequency range of 130.5 GHz to 132.8 GHz with an output power of -12 dBm for designs with small-gate-periphery (45- mu m) HEMTs.<<ETX>>

InGaAs/AlAs/InGaAsP resonant tunneling hot electron transistors grown by chemical beam epitaxy

InP-based resonant tunneling hot electron transistors (RHETs) were studied systematically using chemical beam epitaxy (CBE) for the first time. All the RHETs studied have a highly strained AlAs/In/sub 0.75/Ga/sub 0.25/As/AlAs resonant tunneling double barrier as a hot electron injector, and an InP collector barrier with or without InGaAsP graded layers. The highest transport ratio (/spl alpha/) observed is 0.98, and the highest peak-to-valley current ratios (PVRs) measured are 20 and 200 in the collector current and base current, respectively, at 80 K. A self-consistent simulation is used as a reference to optimize the hot electron injector and to explain the ballistic transport. An energy spectrometer technique was applied to the RHETs for resolving the hot electron energy distribution which showed a full width at half maximum (FWHM) of around 58 meV, indicating ballistic transport of electrons. Finally, room temperature transistor action was also observed with a /spl beta/ of 4 and a cutoff frequency of 31 GHz. >

The growth of resonant tunneling hot electron transistors using chemical beam epitaxy

A systematic growth study of InGaAs/AIA5/InGaAsP resonant tunneling hot electron transistors (RHETs) was performed using chemical beam epitaxy (CBE). The resonant tunneling hot electron transistors studied consist of a highly strained AIAs/1n075Ga525As/AIA5 double barrier structure and an undoped InP collector barrier with 1.1 and 1.2 gm InGaAsP graded layers. These quaternaries were lattice matched to InP within 2.6x iO~ and showed an averaged full width at half-maximum (FWHM) of 6 meV from low temperature photoluminescence (PL) measurement. The effects of growth interrupt were studied using PL, X-ray diffraction and secondary ion mass spectrometry (SIMS) measurements, It was found that excessive growth interrupt induced high oxygen accumulation (8x io’~ cm 3) at the heterojunction and reduced the intensity of PL spectra. Moreover, for the growth of tunneling heterostructures, low substrate temperature, appropriate growth interrupts and use of hydride drying filters and high purity hydrides were helpful to improve device performance. The highest peak-to-valley current ratio (PVR) observed was 12.7, and maximum base transport ratio was 0.98 at 80 K. Furthermore, some digital functions such as flip-flop gate and exclusive NOR were demonstrated using a single RHET.

InAlAs/InGaAs heterojunction bipolar transistors grown by chemical beam epitaxy (CBE)

The authors report an InAlAs/InGaAs heterojunction bipolar transistor (HBT) with an InP etch-stop layer grown entirely by chemical beam epitaxy (CBE). CBE has demonstrated the ability to grow these HBTs in a single, uninterrupted growth sequence. The devices demonstrated uniform DC characteristics that were insensitive to device geometry and perimeter effects. The offset voltage and current ideality factors indicated that rather complex injection mechanisms are occurring in the base-emitter junction. RF performance was limited by parasitic RC charging times and by the transit-time through the thick base-collector depletion region.<<ETX>>

The design of an ECR plasma system and its application to InP grown by CBE

An electron cyclotron resonance (ECR) plasma system has been designed for the purpose of using an excited beam of gases during CBE growth. The system was designed to use hydrogen, nitrogen and argon. An ECR plasma system has the ability to ignite a low pressure and low temperature plasma with very low ion energies, which should minimize any damage to the growing layer. The motivation behind using a plasma during growth is the ability of atomic hydrogen to remove contaminants from the growing layer and to enhance the decomposition of organometallic precursors at low substrate temperatures. InP grown with a hydrogen plasma showed an n-type background carrier concentration of 6.0X1016 cm-3, with a rough surface and a strong photoluminescence peak at 1.378 eV. A control sample grown with excess hydrogen but without the plasma had a background carrier concentration of 1.0X1015 cm-3, a 77 K mobility of 65,000 cm2/V·s and a very weak photoluminescence peak at 1.378 eV. The most likely cause for the layer degradation during plasma growth is an intrinsic defect such as an antisite defect or a vacancy. The n-type nature of the layer and the relatively high carrier concentration would seem to exclude the possibility of carbon or any other unintentional impurities.

Double heterojunction bipolar transistors with chirped InGaAs/InP superlattice base-collector junction grown by CBE

We report the performance of InP DHBTs with a chirped InGaAs/InP superlattice B-C junction grown by CBE. The B-C junction of the DHBT was graded with a 10-period InGaAs/InP chirped superlattice (CSL) between the InGaAs base and the lightly doped InP collector. A highly doped thin layer was also included at the end of the CSL to offset the quasielectric field arising from the grade and suppress further the carrier blocking effect across the B-C heterojunction. The InP/InGaAs CSL DHBT demonstrated a high BV/sub C/F/sub EO/ of 18 V with a typical current gain of 55 with minimal carrier blocking up to high current densities. Maximum cutoff frequencies of f/sub max/=146 GHz and f/sub /spl tau//=71 GHz were obtained from the fabricated 2/spl times/10 /spl mu/m/sup 2/-emitter DHBT.