Joel M. Fastenau

High performance continuous wave 1.3 μm quantum dot lasers on silicon

We demonstrate record performance 1.3 μm InAs quantum dot lasers grown on silicon by molecular beam epitaxy. Ridge waveguide lasers fabricated from the as-grown material achieve room temperature continuous wave thresholds as low as 16 mA, output powers exceeding 176 mW, and lasing up to 119 °C. P-modulation doping of the active region improves T0 to the range of 100–200 K while maintaining low thresholds and high output powers. Device yield is presented showing repeatable performance across different dies and wafers.

Quantum Dashes on InP Substrate for Broadband Emitter Applications

We report on the development of InAs/InGaAlAs quantum-dash-in-well structure on InP substrate for wideband emitter applications. A spectral width as broad as 58 meV observed from both photoluminescence and surface photovoltage spectroscopy on the sample indicating the formation of highly inhomogeneous InAs-dash structure that results from the quasi-continuous interband transition. The two-section superluminescent diodes (SLDs), with integrated photon absorber slab as lasing suppression section, fabricated on the InAs dash-in-well structure exhibits the close-to-Gaussian emission with a bandwidth (full-width at half-maximum) of up to 140 nm at ~ 1.6 mum peak wavelength. The SLD produces a low spectrum ripple of 0.3 dB and an integrated power of ~ 2 mW measured at 20degC under 8 kA/cm2. The oxide stripe laser exhibits wide lasing wavelength coverage of up to 76 nm at ~ 1.64 mum center wavelength and an output optical power of ~ 400 mW from simultaneous multiple confined states lasing at room temperature. This rule changing broadband lasing signature, different from the conventional interband diode laser, is achieved from the quasi-continuous interband transition formed by the inhomogeneous quantum-dash nanostructure.

Barrier-Engineered Arsenide–Antimonide Heterojunction Tunnel FETs With Enhanced Drive Current

In this letter, we experimentally demonstrate enhancement in drive current <i>I</i>_ON and reduction in drain-induced barrier thinning (DIBT) in arsenide-antimonide staggered-gap heterojunction (hetj) tunnel field-effect transistors (TFETs) by engineering the effective tunneling barrier height Eb_eff from 0.58 to 0.25 eV. Moderate-stagger GaAs_0.4Sb_0.6/In_0.65 Ga_0.35As (Eb_eff = 0.31 eV) and high-stagger GaAs_0.35Sb_0.65/In_0.7Ga_0.3As (Eb_eff = 0.25 eV) hetj TFETs are fabricated, and their electrical results are compared with the In_0.7Ga_0.3As homojunction (homj) TFET (Eb_eff = 0.58 eV). Due to the 57% reduction in Eb_eff, the GaAs_0.35Sb_0.65/In_0.7Ga_0.3As hetj TFET achieves 253% enhancement in <i>I</i>_ON over the In_0.7Ga_0.3As homj TFET at <i>V</i>_DS = 0.5 V and <i>V</i>_GS - <i>V</i>_OFF = 1.5 V. With electrical oxide thickness (Toxe) scaling from 2.3 to 2 nm, the enhancement further increases to 350 %, resulting in a record high <i>I</i>_ON of 135 μA/μm and 65% reduction in DIBT at <i>V</i>_DS = 0.5 V.

Interband cascade infrared photodetectors with enhanced electron barriers and p-type superlattice absorbers

We present results on the optical and electrical performance of mid-infrared detectors based on interband-cascade structures. These devices include enhanced electron barriers, designed to suppress intraband-tunneling current between stages, and p-doped type-II InAs/GaSb superlattice absorbers. Within the sample set, we examined devices with different absorber thicknesses and doping levels. Carriers are extracted less efficiently in devices with longer absorbers, which is attributed to more band bending within the absorber due to electric charge accumulation. Also, devices with lower-doped (1 × 1017 cm−3) absorbers are found to have better optical and electrical performances than those with higher levels of doping (3 × 1017 cm−3). The overall performance of these devices was superior to previously reported results, with Johnson-noise limited detectivities, at 4.0 μm, as high as 6.0 × 1012 and 2.5 × 1011 Jones at 80 and 150 K, respectively.

Sub-300 nm InGaAs/InP Type-I DHBTs with a 150 nm collector, 30 nm base demonstrating 755 GHz f max and 416 GHz f T

We report InP/InGaAs/InP double heterojunction bipolar transistors (DHBT) fabricated using a simple mesa structure. The devices employ a 30 nm highly doped InGaAs base and a 150 nm InP collector containing an InGaAs/InAlAs superlattice grade. These devices exhibit a maximum f_max = 755 GHz with a 416 GHz /f_T. This is the highest f_max reported for a mesa HBT. Through the use of i-line lithography, the emitter junctions have been scaled from 500-600 nm down to 250-300 nm -all while maintaining similar collector to emitter area ratios. Because of the subsequent reduction to the base spreading resistance underneath the emitter R_b,spread and increased radial heat flow from the narrower junction, significant increases to f_max and reductions in device thermal resistance θ_JA are expected and observed. The HBT current gain β ≈ 24-35, BV_ceo = 4.60 V, BV_cbo = 5.34 V, and the devices operate up to 20 mW / μm² before self-heating is observed to affect the DC characteristics.

Detection wavelength of InGaAs/AlGaAs quantum wells and superlattices

InGaAs/AlGaAs quantum well structures have been shown to be versatile for infrared detection. By changing the material composition, one can tune the detection wavelength from 2 to 35 μm and beyond. However, there have been few systematic calculations on the absorption wavelength of these structures with respect to their structural parameters. In this work we have adopted the transfer-matrix method to calculate both their energy levels and the wave functions. From this calculation, the absorption and the responsivity spectra of the structures can be predicted. The theory agrees with the experimental result of the test structures. Supported by the experimental evidence, we applied the calculation to a general class of midwavelength detectors and thus established a useful guideline for the detector design in this wavelength range.

InGaAs/InP DHBTs with 120-nm collector having simultaneously high f/sub /spl tau//, f/sub max//spl ges/450 GHz

InP/In/sub 0.53/Ga/sub 0.47/As/InP double heterojunction bipolar transistors (DHBT) have been designed for increased bandwidth digital and analog circuits, and fabricated using a conventional mesa structure. These devices exhibit a maximum 450 GHz f/sub /spl tau// and 490 GHz f/sub max/, which is the highest simultaneous f/sub /spl tau// and f/sub max/ for any HBT. The devices have been scaled vertically for reduced electron collector transit time and aggressively scaled laterally to minimize the base-collector capacitance associated with thinner collectors. The dc current gain /spl beta/ is /spl ap/ 40 and V/sub BR,CEO/=3.9 V. The devices operate up to 25 mW//spl mu/m/sup 2/ dissipation (failing at J/sub e/=10 mA//spl mu/m/sup 2/, V/sub ce/=2.5 V, /spl Delta/T/sub failure/=301 K) and there is no evidence of current blocking up to J/sub e//spl ges/12 mA//spl mu/m/sup 2/ at V/sub ce/=2.0 V from the base-collector grade. The devices reported here employ a 30-nm highly doped InGaAs base, and a 120-nm collector containing an InGaAs/InAlAs superlattice grade at the base-collector junction.

Molecular beam epitaxy growth of metamorphic high electron mobility transistors and metamorphic heterojunction bipolar transistors on Ge and Ge-on-insulator/Si substrates

A direct growth approach using composite metamorphic buffers was employed for monolithic integration of InP-based high electron mobility transistors (HEMTs) and heterojunction bipolar transistors (HBTs) on Ge and Ge-on-insulator (GeOI)/Si substrates using molecular beam epitaxy. GaAs layers nucleated on these substrates and grown to a thickness of 0.5μm were optimized to minimize the nucleation and propagation of antiphase boundaries and threading dislocations, and exhibited an atomic force microscopy rms roughness of ∼9A and x-ray full width at half maximum of ∼36arcsec. A 1.1μm thick graded InAlAs buffer was used to transition from the GaAs to InP lattice parameters. The density of threading dislocations at the upper interface of this InAlAs buffer was ∼107cm−2 based on cross-sectional transmission electron microscopy analyses. HEMT structures grown metamorphically on GeOI/Si substrates using these buffer layers demonstrated transport properties equivalent to base line structures grown on InP substrates...

Role of InAs and GaAs terminated heterointerfaces at source/channel on the mixed As-Sb staggered gap tunnel field effect transistor structures grown by molecular beam epitaxy

The structural, morphological, defect properties, and OFF state leakage current mechanism of mixed As-Sb type-II staggered gap GaAs-like and InAs-like interface heterostructure tunnel field effect transistors (TFETs) grown on InP substrates using linearly graded InxAl1-xAs buffer by molecular beam epitaxy are investigated and compared. Symmetric relaxation of >90% and >75% in the two orthogonal 〈110〉 directions with minimal lattice tilt was observed for the terminal GaAs0.35Sb0.65 and In0.7Ga0.3As active layers of GaAs-like and InAs-like interface TFET structures, respectively, indicating that nearly equal numbers of α and β dislocations were formed during the relaxation process. Atomic force microscopy reveals extremely ordered crosshatch morphology and low root mean square roughness of ∼3.17 nm for the InAs-like interface TFET structure compared to the GaAs-like interface TFET structure of ∼4.46 nm at the same degree of lattice mismatch with respect to the InP substrates. The GaAs-like interface exhibit...

High Performance Mixed Signal and RF Circuits Enabled by the Direct Monolithic Heterogeneous Integration of GaN HEMTs and Si CMOS on a Silicon Substrate

In this work we present recent results on the direct heterogeneous integration of GaN HEMTs and Si CMOS on a silicon substrate. GaN HEMTs whose DC and RF performance are comparable to GaN HEMTs on SiC substrates have been achieved. As a demonstration vehicle we designed and fabricated a GaN amplifier with pMOS gate bias control circuitry (a current mirror) and heterogeneous interconnects. This simple demonstration circuit is a building block for more advanced RF, mixed signal and power conditioning circuits, such as reconfigurable or linearized PAs with in-situ adaptive bias control, high power digital-to-analog converters (DACs), driver stages for on-wafer optoelectronics, and on-chip power distribution networks.