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We investigate the use of low-threshold 980-nm vertical-cavity surface-emitting lasers for free-space optical interconnects. The vertical-cavity surface-emitting lasers and backilluminated detectors are monolithically integrated with microlenses on the back sides of the growth substrates to eliminate the necessity of external optics. With a channel pitch of 250 [[micro]meter], an interconnect length between boards of the order of 5 to 10 mm with a [+ or -]50-[[micro]meter] lateral alignment tolerance can be achieved without external relay optics. The complete link is modeled to predict the system's efficiency and maximum bit rate. Data transmission at 500 Mbits/s per channel is demonstrated. The data rate was limited by parasitics, not the inherent bandwidth of the laser diodes. OCIS codes: 200.4650, 140.3460, 220.3630, 350.3950.

Tensile-strained Ge is a possible laser material for Si integrated circuits, but reports of lasers using tensile Ge show high threshold current densities and short lifetimes. To study the origins of these shortcomings, Ge ridge waveguides with tensile strain in three dimensions were fabricated using compressive silicon nitride (SiNx) films with up to 2 GPa stress as stress liners. A Raman peak shift of up to 11 cm-1 was observed, corresponding to 3.6% hydrostatic tensile strain for waveguides with a triangular cross-section. Real time degradation in tensile-strained Ge was observed and studied under transmission electron microscopy (TEM). A network of defects, resembling dark line defects, was observed to form and propagate with a speed and density strongly correlated with the local strain extracted from both modeled and measured strain profiles. This degradation suggests highly tensile-strained Ge lasers are likely to have significantly shorter lifetime than similar GaAs or InGaAs quantum well lasers. [ABSTRACT FROM AUTHOR]

InGaAs/InP DHBTs are fabricated using electron-beam lithography to define the emitter and base mesas. Emitter mesas 150 nm wide, and base mesas with < 25 nm misalignment to the emitter have been developed. Emitter contacts are prepared through blanket, refractory metal evaporation to obtain emitter contact resistivity ρex = 2 Ω·µm2. This low record resistivity, combined with the narrow emitter and base mesas, enables device RF performance of simultaneous fτ and fmax of 530 GHz and 750 GHz, respectively, at a power density of > 40 mW/µm2. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

A novel method of fabricating compact intra-cavity contacts with high yield for GaAs/AlGaAs-based vertical-cavity surface-emitting lasers is presented. By carefully tailoring the composition of high-aluminum content layer, a highly selective Al2O3 etch-stop layer can be formed simultaneously with the oxide aperture during wet thermal oxidation. With this technique, contact metals can be uniformly deposited on deeply embedded contact layers over large substrate areas. Utilizing this embedded etch-stop design, dual intra-cavity contacted three-terminal vertical-cavity surface-emitting lasers were fabricated, demonstrating submilliampere threshold currents, over 54% differential quantum efficiencies and over 9 mW output powers. [ABSTRACT FROM AUTHOR]

We report raised source/drain (S/D) InAs quantum well MOSFETs incorporating a vertical spacer formed by metal–organic chemical vapor deposition epitaxial regrowth. By adopting a 12-nm-thick vertical spacer between the channel and the N+S/D , off-state characteristics are significantly improved. A device with a 40-nm- Lg and 12-nm-thick spacer shows 2.5- mS/\mum peak transconductance (gm) , 86-mV/decade subthreshold swing at VDS=0.5~V , 83-mV/V drain-induced barrier lowering, and 482- \muA/\mum ON-current at 100- nA/\mum OFF-current and VDD=0.5~V . In addition, a 3.0- mS/\mum peak gm at VDS=0.5~V is achieved in an 18-nm- Lg device with a 2-nm-thick spacer, the highest reported peak gm of any field-effect transistor. [ABSTRACT FROM AUTHOR]

We report enhancement-mode composite-channel (\In0.53 \Ga0.47\As/\InAs/\In0.53\Ga0.47\As) MOSFETs fabricated using a substitutional-gate process, with \n^+ relaxed InAs source–drain regions formed by regrowth by molecular beam epitaxy. A device with 70-nm gate length and 2-nm \In0.53\Ga0.47\As/3.5-nm InAs/3-nm \In0.53\Ga0.47\As channel showed a peak transconductance of greater than 0.76 \mS/\mu\m at Vds = \0.4\ \V and showed Id = \0.5\ \mA/\mu\m at Vds = \0.4\ \V and Vgs - Vth = \0.7\ \V. The subthreshold swing at Vds = \0.1\ \V was 130 mV/dec. [ABSTRACT FROM PUBLISHER]

We report gate-first enhancement-mode (E-mode) N-polar GaN MISFET devices with self-aligned source/drain regions by molecular beam epitaxy regrowth and with a \SiNx gate dielectric. E-mode operation at Vds = \4.0\ V is demonstrated for devices with gate \lengths > \0.18 \ \mu\m with a 20-nm GaN channel and a high-temperature \SiNx gate dielectric. A high drain current of 0.74 A/mm was measured for an Lg = \0.62-\mu\m device with a peak transconductance of 225 mS/mm and a positive threshold voltage of 1 V. The on resistance of the device was 2 \Omega\cdot\mm. Devices show short-channel effect with decreasing gate lengths. [ABSTRACT FROM AUTHOR]

We report an \InP/In0.53\Ga0.47\As/InP double heterojunction bipolar transistor (DHBT) demonstrating simultaneous 430-GHz f\tau and 800-GHz f \max. The devices were fabricated using a triple mesa process with dry-etched refractory metals for emitter contact formation. The devices incorporate a 30-nm-thick InP emitter semiconductor which enables a wet-etch emitter process demonstrating 270-nm-wide emitter–base junctions. At peak RF performance, the device is operating at 30 \mW/\mu\m^2 with Jc = \18.4\ \mA/\mu\m^{2} and Vce = \1.64\ \V. The devices show a peak DC common-emitter current gain (\beta) \sim \20 and VBR, {CEO} = \2.5\ \V. [ABSTRACT FROM AUTHOR]

We report Al2O3/In0.53Ga0.47As MOSFETs having both self-aligned in situ Mo source/drain ohmic contacts and self-aligned InAs source/drain n+ regions formed by MBE regrowth. The device epitaxial dimensions are small, as is required for 22-nm gate length MOSFETs; a 5-nm In0.53Ga0.47As channel with an In0.48Al0.52As back confinement layer and the n++ source/drain junctions do not extend below the 5-nm channel. A device with 200-nm gate length showed ID = 0.95 mA/μm current density at VGS = 4.0 V and gm = 0.45 mS/μm peak transconductance at VDS = 2.0 V. [ABSTRACT FROM AUTHOR]