H. Zhao

Ultralow threshold current vertical-cavity surface-emitting lasers with AlAs oxide-GaAs distributed Bragg reflectors

An electrically-pumped, vertical-cavity, surface-emitting laser (VCSEL) using an AlAs oxide-GaAs DBR above the AlGaAs-GaAs-InGaAs gain region and a conventional AlAs-GaAs DBR below is described. By selective oxidation, devices with current flow apertures of different areas are fabricated, and in 8-/spl mu/m-square devices, threshold currents as low as 0.22 mA are achieved. Being the first electrically-pumped VCSEL to utilize the oxide-based DBR, it demonstrates that the oxide-based DBR is of sufficient quality to realize submilliampere threshold currents.<<ETX>>

Microcavity effects on the spontaneous emission from InGaAs/GaAs quantum wells

The spontaneous emission from an InGaAs/GaAs single‐quantum well surrounded by AlAs/GaAs distributed Bragg reflectors (DBR) under the near‐resonance condition between the exciton level and the confined optical mode is investigated. Under such conditions, on‐axis spontaneous emission enhancement at the cavity resonant wavelength is clearly identified. The strength and character of the interaction of the exciton with the confined optical mode is determined by the dependence of photoluminescence spectra on the reflectivity of the DBR. Temperature dependence of the enhanced spontaneous emission shows the cavity resonant wavelength shifts at 0.85 A/°C around room temperature. An increase of emission intensity at the cavity resonant wavelength with increasing temperature is also observed, which can be related to the increase of the interaction between excitonic emission and cavity mode.

Lock‐on effect in pulsed‐power semiconductor switches

Certain high‐voltage pulsed‐power switches based on semi‐insulating GaAs or InP exhibit a ‘‘lock‐on’’ effect. In this paper, this effect is argued to be fundamentally a transferred‐electron effect, and its experimentally observed characteristics are explained. The lock‐on effect causes high forward drop and high power dissipation for certain pulsed‐power switches based on GaAs and various other direct‐gap materials.

High efficiency InGaAs/GaAs single-quantum-well lasers using single-step metalorganic chemical vapor deposition

Low-threshold-current single-quantum-well InGaAs/GaAs lasers are fabricated by metalorganic chemical vapor deposition on a nonplanar substrate. By taking advantage of the growth rate and doping differences on different crystal facets during the growth, a buried heterostructure laser with natural current blocking p-n-p-n junction is formed by a single growth step. Threshold currents as low as 1.0 mA under pulsed operation and 1.2 mA under continuous-wave operation are obtained for uncoated lasers at room-temperature. The lasers showed high external quantum efficiency (80%) and high T/sub 0/ (150 K). High reflection coated laser (95%/95%) have CW threshold current as low as 0.28 mA.<<ETX>>

High-speed large-signal digital modulation of three-terminal low-threshold strained InGaAs/GaAs lasers

We present large-signal digital modulation of very low-threshold strained InGaAs/GaAs single quantum well (SQW) lasers with monolithically integrated intracavity modulators. The voltage controlled intracavity modulator was driven from a simple emitter-follower using a single NPN transistor. Modulation response mas obtained from dc to 1 Gbit/s with a modulation efficiency of 27% and modulation depth of nearly 100%. A bit-error-rate (BER) lower than 10/sup -11/ was measured at 1 Gbit/s with an input signal swing of only 110 mV. We demonstrate the suitability of these devices for ultrabroad-band optical interconnection applications.<<ETX>>

A high-voltage optoelectronic GaAs static induction transistor

Experimental realization of an optically activated, high-voltage GaAs static induction transistor (SIT) is reported. In the forward blocking state, the breakdown voltage of the device was approximately 200 V, while in the conduction state, on-state current densities exceeding 150 A/cm/sup 2/ were obtained. In the floating-gate configurations (gate open), the specific on-resistance of the device was approximately 50 m Omega -cm/sup 2/. Optical modulation of the device was achieved using a compact semiconductor laser array as the triggering source. In this mode, a gate-coupled RC network was implemented, resulting in an average switching energy gain (load energy/optical energy) of approximately 30. This mode of operation is applicable to series-coupled devices for pulsed switching at higher power levels.<<ETX>>

A comparative study of Si‐ and GaAs‐based devices for repetitive, high‐energy, pulsed switching applications

A study is performed to assess Si and GaAs as materials for realization of repetitive, high‐energy, pulsed switches in applications where the switching parameters are blocking voltages (VB) exceeding 1 kV in the off state and conduction currents (IF) in excess of 500 A in the on state, the current risetime being less than 1 μs and the pulse length being longer than 50 ns. Theoretical and technological limitations associated with the switching characteristics of Si‐ and GaAs‐based majority carrier (unipolar) and minority carrier (bipolar) devices in the low‐field, high‐mobility, and high‐field velocity saturation regimes are analyzed and discussed. It is concluded that for medium power applications (VBIF<300 kW,VB≳1 kV), majority carrier devices are best suited for fast switching processes in the low‐field, low current density (J<100 A/cm2) regime. Under such conditions, the high drift mobility of GaAs allows for realization of field‐effect devices exhibiting fast switching speeds and low on‐state conducti...

Three-terminal bistable low-threshold strained InGaAs/GaAs laser grown on structured substrates for digital modulation

Strained InGaAs/GaAs quantum-well three-terminal lasers with monolithically integrated intracavity modulators were fabricated using low threshold current structures formed by the temperature engineered growth (TEG) technique. An on-off switching ratio of 556 was obtained for a 30-mV change in absorber voltage. An optical power contrast ratio of 7.5 was measured with a total DC power consumption of 25.3 mW. These results show a great improvement in the digital (on-off) switching performance of three-terminal lasers with intracavity modulators.<<ETX>>

Growth and doping properties of AlGaAs/GaAs/InGaAs structures on nonplanar substrates for applications to low threshold lasers

Abstract The growth behavior of AlGaAs/GaAs/InGaAs structures on non-planar (100) GaAs substrates has been studied. The structures were grown by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) on substrates which have mesa stipes aligned along the ( 1 10) direction with (100) mesa tops and (111)A sidewalls. The growth rates and the doping of the AlGaAs/GaAs/InGaAs layers are shown to have a strong dependence on the crystallographic orientation as the sidewall approaches the (111)A plane. Growth temperature and III–V ratio also affect the relative growth rate and the doping of the layers. Using the above properties, we have grown and fabricated low threshold InGaAs/GaAs QW lasers by a single step MOCVD growth. Threshold current as low as 0.5 mA for uncoated DQW lasers has been achieved.

Submilliampere threshold current InGaAs-GaAs-AlGaAs lasers and laser arrays grown on nonplanar substrates

High performance buried heterostructure InGaAs-GaAs-AlGaAs quantum-well lasers and laser arrays with tight spatial confinement of the electrical current and the optical fields have been fabricated by metalorganic chemical vapor deposition. The lasers ace fabricated in a single growth step, using nonplanar substrates as a template for the active region definition. CW room temperature threshold currents, as low as 0.5 mA and 0.6 mA, are obtained for as-cleaved double and single quantum-well lasers, respectively. External quantum efficiencies exceeding 80% are obtained in the same devices. High-reflectivity facet-coated lasers have room temperature CW threshold currents as low as 0.145 mA with 10% external quantum efficiency. Lasers made by this technique have high yield and uniformity, and are suitable for low threshold array applications. >