Double heterojunction GaAs/GaAlAs I2L inverter

GaAs/GaAlAs double heterojunction I2L inverters with a vertical pnp current source were fabricated by ion implantation and Zn-diffusion into LPE structures. The current gain of the upside-down-operated double heterojunction npn transistor has been improved by a factor of two compared to the gain of the npn transistor of the otherwise similar structure. In addition, the wide-gap junction pnp transistor gives a solution to the critical switch-on problem which can occur when a wide-gap emitter transistor is used for the switching transistor.     

Kink-free narrow-stripe proton-isolated GaAlAs/GaAs injection lasers

Totally kink-free and very-narrow-stripe proton-isolated injection lasers are presented. The standard gold-indium metal-contact bonding system has been investigated, and as a result an improved bonding technique is presented. Kink-free lasers with output power up to 20 mW have been accelerated at 80°C ambient for 1000 h without any change in thermal resistance and with an expected lifetime of above 106 h at room temperature.     

Application of thermal pulse annealing to ion-implanted GaAlAs/GaAs heterojunction bipolar transistors

Post-implant anneals of short (10-15 s) duration are compared with extended (10 min) furnace anneals for the fabrication of Be-implanted MBE-grown GaAlAs/GaAs heterojunction bipolar transistors. It is shown that the thermal pulse anneals can lead to improved Be-implant electrical activation in Ga0.7Al0.3As and GaAs, to improved contact resistance to Be-implanted GaAs, and to improved transistor characteristics. The transistor improvement is inferred to be due to a reduction in diffusion of the grown-in dopant profile.     

Fabrication of tapered couplers in GaAs/GaAlAs rib waveguides

Tapered couplers have been fabricated in GaAs/GaAlAs single-mode rib waveguides. A new etching technique has been used to fabricate transitions of 1 μm over lengths of approximately 160 to 300 μm. Losses for the TE and TM fundamental modes have been measured at a wavelength of 1.3 μm     

Pulsed oscillation of GaAlAs/GaAs surface-emitting injection laser

We report the fabrication and lasing properties of the first GaAlAs/GaAs surface-emitting injection laser. The threshold current was 330 mA for 20 ?m? electrode at 77 K under pulsed conditions (? = 7960 ?). In some devices we achieved room temperature pulsed oscillation.     

Fabrication of integrated injection logic with electron-beam lithography and ion implantation

Integrated injection logic gates have been fabricated using electron-beam lithography and ion implantation. A factor of five reduction in gate area over conventional designs was achieved by using minimum linewidths of 1.25 µm. Average propagation delay of 6 ns at 100 µA/gate injector current and speed-power product of 0.13 pJ at 5 µA have been measured on five collector, stick geometry, n⁺guard ring device structures. The delay time is a factor of three and the speed-power product is a factor of five better than typical conventionally sized structures fabricated with photolithography. A minimum delay of 3.6 ns has been achieved on five collector device structures designed for maximum speed.     

Coherence of a room-temperature CW GaAs/GaAlAs injection laser

The temporal coherence of a stripe-geometry double-heterojunction GaAs/GaAlAs laser operating CW at room temperature was determined. A heterodyne detection scheme was used involving the mixing of the laser field with a frequency-shifted and time-delayed image of itself in an interferometer. Because the laser device oscillated in several longitudinal modes, the autocorrelation function of its output exhibited resonances for specific time delays. The rate at which the amplitude of these resonances decreased with increasing time delays provided a measure of an apparent coherence length associated with individual longitudinal modes. The coherence length, so defined, was found to increase linearly with drive current in excess of threshold. This observation is interpreted as evidence that the intrinsic linewidth of a longitudinal mode is inversely proportional to the coherent optical power in that mode. Apparent coherence lengths were a few centimeters for a few milliwatts of total optical power emitted per facet. For a perfectly balanced interferometer, a sharp heterodyne beat signal was also observed when the laser device was operated considerably below threshold, i.e., in the LED mode.     

Double heterojunction GaAlAs/GaAs I/sup 2/L integrated circuits

The fabrication and DC characterisation of GaAlAs/GaAs double heterojunction bipolar transistors (DHBTs) grown by molecular beam epitaxy are described. This baseline process has been developed for the implementation of heterojunction integrated injection logic (HI/sup 2/L) integrated circuits. Results concerning an I/sup 2/L ring oscillator and a divide-by-two circuit are given.<>     

Backgate-induced characteristics of ion-implanted GaAs MESFET's

Three important characteristics of GaAs ion-implanted MESFET's associated with the phenomenon of backgating have been identified and measured. These include a negative backgate capacitance, initiation and/or control of low-frequency oscillations, and enhancement of g-r noise, all related to the deep-level electron traps present in the semi-insulating substrate beneath the implanted layer. Low-frequency oscillations have been observed mostly in devices with high gate-leakage current under conditions involving zero to large negative backgate bias. The frequency of oscillations and the backgate negative-capacitance magnitude have been found to decrease and increase, respectively, with the increase of the negative backgate bias voltage. This implies a decrease in the capture/emission cross section of traps at high fields.     

沟道SI－GaAs衬底上正装GaAlAs／GaAs BH激光器的制作

介绍了宽沟道ＳＩ－ＧａＡｓ衬底上的ＢＨ激光器的制作，全部结构由两次外延形成，阈值电流为５５ｍＡ。在Ｉ＝２Ｉｔｈ时，Ｐ－Ｉ曲线仍保持良好的线性关系。     

Luminescence of stepped quantum wells in GaAs/GaAlAs and InGaAs/GaAs/GaAlAs structures

Luminescence spectra of doped and undoped GaAs/GaAlAs and InGaAs/GaAs/GaAlAs structures containing several tens of stepped quantum wells (QW) are investigated. The emission bands related to free and bound excitons and impurity states are observed in QW spectra. The luminescence excitation spectra indicate that the relaxation of free excitons to the e1hh1 state proceeds via the exciton mechanism, whereas an independent relaxation of electrons and holes is specific to bound excitons and impurity states. The energy levels for electrons and holes in stepped QWs, calculated in terms of Kane’s model, are compared with the data obtained from the luminescence excitation spectra. The analysis of the relative intensities of emission bands related to e1hh1 excitons and exciton states of higher energy shows that, as the optical excitation intensity increases, the e1hh1 transition is more readily saturated at higher temperature, because the lifetime of excitons increases. Under stronger excitation, the emission band of electron-hole plasma arises and increases in intensity superlinearly. At an excitation level of ～10⁵ W/cm², excitons are screened and the plasma emission band dominates in the QW emission. Nonequilibrium luminescence spectra obtained in a picosecond excitation and recording mode show that the e1hh1 and e2hh2 radiative transitions are 100% polarized in the plane of QWs.     

Structure dependent axial mode stability in GaAlAs/GaAs injection lasers

The influence of structure on the saturation behaviour of mode gain and the axial mode stability is investigated for different types of AlGaAs injection lasers. Both experimental and theoretical results confirm that carrier confinement along the lateral direction is effective for axial mode stabilisation.     

Calculation of I/V characteristics for ion-implanted GaAs MESFETs

The DC characteristics of an ion-implanted MESFET have been calculated from theoretical and measured carrier concentration profiles. The calculation allows the determination of characteristics for planar or recessed gate structures and shows good agreement with experimental devices.     

Planar GaAs MOSFET integrated logic

Selective and multiple ion implantations directly into a semi-insulating GaAs substrate were utilized to fabricate planar integrated circuits with deep-depletion plasma-grown native oxide gate GaAs MOSFET's. 1.2-µm gate 27-stage enhancement/depletion (E/D) type ring oscillators, with the circuit optimized to reduce parasitic capacitance, were fabricated (using conventional photolithography) to assess the speed-power performance in digital applications. A minimum propagation delay of 72 ps with a power-delay product of 139 fJ was obtained, making these devices the fastest among current GaAs and Si logic fabricated by conventional photolithography. A minimum power-delay product of 36 fJ with a propagation delay of 157 ps was obtained. The power-delay product is comparable with that of 1.2-µm gate GaAs E-MESFET logic, and the speed is more than twice as great. This paper includes a comparison of the theoretical cut off frequency of MESFET and MOSFET logic devices operating in depletion mode. Results indicate that MOSFET logic has superior potential for high-speed operation.     

Backgating and light sensitivity in ion-implanted GaAs integrated circuits

Ion-implanted GaAs integrated circuits have been characterized under dark and illuminated conditions to determine the sensitivity of ac parameters to light. Auxiliary experiments were performed on discrete IC elements using white and monochromatic illumination and backgating. Discrete MESFET's were characterized under the various conditions to determine corresponding variations in the magnitudes of Sehottky-barrier height and parasitic channel resistances. We have determined that light sensitivity and backgating are strongly interrelated and arise from a depletion layer at the substrate active-layer interface. We will describe the effect of trap filling on channel resistance and the resulting speed-power variations arising from illumination and backgating.     

GaAs/GaAlAs active-passive-interference laser

A GaAs/GaAlAs interference laser with an active and a passive section is reported. A very clean single longitudinal mode is obtained and maintained without mode hopping over about 10°C, which results from the combined effect of interference and real index waveguiding in the lateral direction.     

Fabrication of GaAlAs/GaAs gain-coupled distributed feedback lasersusing the nature of MBE

Molecular beam epitaxy (MBE) regrowth on a corrugated surface is improved dramatically using a novel technique by which not only a clean surface can be obtained but also the shape of grating can be precisely controlled. A GaAlAs/GaAs multi-quantum well gain-coupled distributed feedback (DFB) laser with an absorptive grating is fabricated all by MBE for the first time. DFB mode oscillation within a range of at least 80°C is achieved. Stable single longitudinal mode oscillation is maintained up to 20 mW     

High bit rate modulation of narrow-stripe proton-implanted GaAs/GaAlAs injection lasers

High bit rate modulation up to 2 Gbit/s of a narrow -stripe (3 ?m) proton-implanted injection laser using resonance oscillation has been achieved. These results indicate that the narrow-stripe laser has possibilities of high bit rate modulation comparable to the broad-stripe laser. To obtain optimum modulation conditions, pulse height distortion was studied for various bias and pulse currents. Optimum was found for a bias current 5% above threshold and a pulse current of 42 mA in a laser with a threshold current of 111 mA.     

Temporal and spectral characteristics of rapidly gain-switched GaAs/GaAlAs buried-heterostructure lasers

The temporal and spectral output of GaAs/GaAlAs buried-heterostructure lasers under excitation with 60 ps electrical pulses is investigated for different DC bias conditions. Optical pulses comparable in width to the electrical pulses can be obtained only if the DC bias is below or close to threshold, where multimode emission is observed. For DC bias well above threshold the laser remains single-mode; however, the optical pulses are considerably broadened.     

Nonsaturated integrated injection logic

Conventional integrated-injection-logic structures suffer from strong saturation of the n?p?n transistors. This increases the storage time, and hence puts a limitation on the propagation delay of the structures. A current-control technique is given to reduce this effect without changing the basic i.i.l. structure.