Reliability of 0.87 µm (Al,Ga)As double heterostructure lasers with Ga(As,Sb) active layers

Double-heterostructure injection lasers with additions of 1% Sb to the GaAs active layer have been found to have significantly improved reliability compared to lasers with binary GaAs active layers. Lasers with extrapolated room temperature median lifetimes of 10⁵hours have Ga(As,Sb) active layers that are lattice matched to the Al0.4Ga0.6As confinement layers. Furthermore, the addition of Sb to the LPE active layer growth melt apparently improves the initial nucleation and growth uniformity of the active layer.     

Observations of negative resistance associated with superlinear emission characteristics of (Al, Ga) As double-heterostructure lasers

Observations are reported of the electrical and optical behavior exhibited by stripe-geometry, proton-bombardment-delineated, (Al, Ga)As double-heterostructure junction lasers, whose output power shows an abrupt, nearly discontinuous increase as a function of input current. When operated within this superlinear regime (in addition to exhibiting self-induced intensity pulsations) the output power averaged over many pulsations fluctuates randomly between levels corresponding to the intensities at either end of the superlinear range. A negative resistance which is light induced and associated with the lasing optical field accompanies the superlinearity, as does motion of the lasing filament along the junction plane. The low temperature behavior of the negative resistance shows that non-ohmic conduction mechanisms are present in the laser material. However, axially nonuniform changes in the luminescence observed through the substrate indicate that saturable optical absorption in the active layer at the laser mirror faces may be the predominate cause of the superlinearity and negative resistance. The development of these effects with aging may be arrested by mirror facet coatings applied before bonding.     

Submicron p-channel (Al,Ga)As/(In,Ga)As HIGFETs

Submicron p-channel (Al,Ga)As/(In,Ga)As HIGFETs have been optimized for application to high-performance complementary GaAs circuits. Major issues with submicron and deep submicron (L_g⩽0.5-μm) P-channel HIGFETs have been the severe short-channel effects, such as high subthreshold leakage currents and high output conductances. With optimization of the p-type self-aligned implant schedule, control of impurity contamination at the substrate/buffer interfaces and increase of the resistivity of the unintentionally-doped GaAs buffers, high-performance submicron devices have been realized. Typically, 0.5-μm P-HIGFETs yielded room temperature transconductances of 90 mS/mm, drain currents at V_gs =V_ds=-1.5 V of 63 mA/mm, and subthreshold leakage currents near 1 nA. Subthreshold slope of 90 mV/decade and output conductances under 5 mS/mm were realized     

High-performance self-aligned (Al,Ga)As/(In,Ga)As pseudomorphicHIGFETs

Transconductance as high as 676 mS/mm at 300 K was observed to 0.7×10-μm² n-channel devices (HIGFETs) made on epilayers with Al_0.3Ga_0.7As insulator thickness of 200 Å and In_0.15Ga_0.85As channel thickness of 150 Å. An FET K value (K=W_g Uε/2aL_g) as large as 10.6 mA/V ² was also measured from another device with transconductance of 411 mS/mm. The high K values are achieved under normal FET operation without hole-injection or drain-avalanche breakdown effects. These results demonstrate the promise of pseudomorphic (Al,Ga)As/(In,Ga)As HIGFETs for high-performance circuit applications     

A possible model for sustained oscillations (pulsations) in (Al,Ga)As double-heterostructure lasers

A model explaining the origins of sustained oscillations in (Al,Ga)As double-heterostructure lasers is proposed and plausibility arguments of its applicability are given. The model relies on saturable-absorberQ-switching to produce the pulsations, with the saturable absorption located near the ends of the laser in regions where surface recombination reduces the injected-carrier density. The sides of the active volume, or defects which cause carrier recombination within the active volume, may also cause such pulsations according to this model.     

GaAs/(Ga,Al)As heterojunction bipolar transistors with buried oxygen-implanted isolation layers

A simple self-aligned technique using oxygen implants to reduce the extrinsic base-collector capacitance in GaAs/(Ga,Al)As heterojunction bipolar transistors (HBT's) is described. This technique has been used to achieve nonthreshold logic ring-oscillators with propagation delays down to 30 ps per gate, the lowest reported to date for any bipolar transistor circuit.     

(Al,Ga)Sb long-wavelength distributed Bragg reflectors

The authors have grown long-wavelength distributed Bragg reflectors (DBRs), using alternating layers of the semiconductors AlSb and (Al,Ga)Sb, and measured their properties. The large refractive index ratio available with these materials allows for high-reflectivity mirrors with relative few mirror pairs. A simple 10-period AlSb/GaSb DBR had a maximum reflectivity of over 98% at a wavelength of 1.92 μm, and a 12-period Al_0.2Ga_0.8Sb/AlSb DBR exhibited reflectance greater than 99% at 1.38 μm. These structures are easily grown by molecular beam epitaxy (MBE) and are suitable for use in surface-normal photonic devices operating at long wavelengths     

High resistivity interfacial layers due to compensation by Sulfur in (Al,Ga)As devices

In p-n junctions grown by LPE in the (Al,Ga)As system, high concentrations of Sulfur can accumulate on the p side of the junction. As a result, a closely compensated, high resistivity region can extend for 0.1-1.0 µm into the p layer. Since sulfur creates deep electron traps in Al0.4Ga0.6As with a thermal activation energy in bulk p-type material of 0.2 eV, both electrical and optical properties of (Al,Ga)As diode devices can be affected by the interfacial sulfur concentrations.     

Radiation damage and annealing behaviour in Be+-implanted pure Ga(Al)Sb layers

Implantation of Be⁺ ions into GaAISb epilayers is used to realize thep ⁺ layer of the Ga_0.96Al_0.04Sb p⁺/Ga_0.96Al_0.04Sbn ⁻ /GaSbn ⁺ (1.55 /Μm) avalanche photodetector whose performances are detailed in Ref. (1). The GaAISb layers are grown using liquid phase epitaxy (LPE); the quality of these as-grown layers is shown through photoluminescence and channeling measurements. The last part of this paper is devoted to the damaging level in the Be⁺-implanted layers. Some annealing techniques are presented as a mean of restoration of the implanted layers. It is clear from the results that the Be⁺ ion implantation leads to a low damage level in this III-V compound.     

Statistical analysis of aging-induced degradation (or lifetime) variation in (Al, Ga)As/GaAs double-heterostructure lasers

Aging-induced degradation, defined as optical power decrease during constant current aging, is obtained for a number of (Al, Ga)As double-heterostructure lasers taken from sixty routinely grown wafers (20-30 devices per wafer). These aging characteristics are statistically analyzed wafer by wafer in correlation with initial laser parameters (or initial operating condition), i.e., CW threshold current, differential quantum efficiency, electrical resistance, nominal temperature sensitivity of threshold current, lasing wavelength, and driving current at aging. The multiple factor analysis evolved during this study reveals that degradation in average lasers can be substantially correlated to a new composite parameter defined as a linear combination of the above parameters. This fact suggests the feasibility of statistical estimation of laser degradation utilizing only the initial parameters. Of the parameters employed, driving current is revealed to be most strongly and commonly associated with laser degradation. To understand the role of driving current in causing lifetime scatters between individual lasers, a possible local heating model is developed. The lifetime scatters experimentally observed are well explained using this model.     

电流密度分布对GaAs/GaAlAs条形激光器的瞬态温度特性的影响

本文将电流密度的侧向分布考虑到热传导模型中去,对一般条形半导体激光器的体内瞬态温度分布进行了计算,同时,利用光谱法对一些条形激光器的瞬态温度进行了实验测量.计算结果同测量结果一致.     

The influence of interface grading on threshold current density of (near) visible DH(Ga,Al)As lasers

The effect of interface grading around the active layer in DH (Ga, Al) As near-visible lasers (lambda_{L} approx 780nm) has been investigated for Ge and Sn as p- and n-type dopants. The combination of graded transition layers with a rather high Al and Ge concentration gives rise to a high effective interface recombination velocity (S lsim 4000cm/s) due to carrier loss in the highly Ge-doped p-Ga0.55Al0.45As cladding layer. The chemical widthWmin{90}max{10}of the transition layers is determined by SIMS and SAES and found to range between 50 and 2.5 nm. The latter extremely steep interfaces have been grown in a novel LPE growth system. The threshold current density and its temperature sensitivity, in terms of the exponential relationshipJ_{th}(T) = J_{0} exp (T/T_{0})improve significantly with abrupt junctions. From this material 5 μm proton-bombarded stripe lasers with a threshold current of ∼90 mA and aT_{0} = 120K at 780 nm have been fabricated.     

Self-aligned modulation-doped (Al,Ga)As/GaAs field-effect transistors

The first modulation-doped (Al,Ga)As/GaAs field-effect transistors (MODFET's) have been fabricated using a self-aligned ion-implantation process. Measured extrinsic transconductances of 190 mS/mm were achieved at 300 K with source resistances of 1 Ω.mm. The highest currents yet reported for such device structures, in excess of 350 mA/mm, were obtained. A value of the maximum two-dimensional electron gas concentration of nearly 1.2 × 10¹²cm^-2was obtained from an analysis of the FET drain current-voltage characteristics using the charge-control model. These results hold promise for the practical fabrication of very high speed integrated circuits based on MODFET's, using a completely planar self-aligned ion-implantation process.     

p-Channel (Al,Ga)As/GaAs modulation-doped logic gates

The operation of logic gates composed of modulation-doped field-effect transistors based on two-dimensional hole-gas conduction is reported for the first time. Direct coupled inverters fabricated on an MBE grown Be-doped (Al,Ga)As/GaAs wafer having a sheet density of 1.5 × 10¹²cm^-2and a 77K mobility of 1800 cm²/V.s exhibit logic states of -0.25 and -0.98 V at 77K for a - 1-V bias. Propagation delays of 233.0 ps/gate are obtained at 77K in ring-oscillator circuits with a power dissipation of 0.31 mW/gate. Power-delay products as low as 9.1 fJ are also obtained.     

Rectification at n-n GaAs:(Ga,Al)As heterojunctions

n-n Ga0.7Al0.3As: GaAs heterojunction structures have been grown by l.p.e., with 1 × 1015 cm-3 net carriers in the ternary. N/W profiling across the heterojunction shows an accumulation region on the GaAs side and a depletion region on the (Ga, Al)As side. I/V characteristics at room temperature show significant rectification.     

Complementary p-MODFET and n-HB MESFET (Al,Ga)As transistors

A complementary transistor structure that utilizes a p-channel modulation-doped FET (p-MODFET) to produce improved p-channel characteristics if reported for the first time. The structure also includes a new type of n-channel MESFET in which the electrons are confined by an n-p heterojunction barrier (n-HB MESFET). The complementary transistor pair is fabricated on a novel MBE-grown n-GaAs/p-(Al,Ga)As/i-GaAs heterostructure. The experimental current-voltage characteristics are presented and demonstrate that this is a promising approach for the development of GaAs-based high-speed complementary logic circuits.     

Energy band diagram and energy band offsets of Ga0.6Al0.4As0.034Sb0.966(p)/Ga0.6Al0.4As0.034Sb0.966(n)/InAs0.9Sb0.1 double interface determined by capacitance-voltage measurements

In this work, we report on the determination of band discontinuities and energy band diagram of the Ga_0.6Al_0.4As_0.034Sb_0.966(p)/Ga_0.6Al_0.4As_0.034Sb_0.966(n)/InAs_0.9Sb_0.1 double interface at equilibrium and room temperature, by capacitance-voltage measurements (C-V). Mesa diodes, with three different diameters are characterized and physical quantities like doping concentration in the unintentionally doped (n.i.d) InAsSb material and diffusion potentials at interfaces are extracted from C-V data. Finally, the energy band diagram of the structure is drawn and experimental values of energy band offsets are deduced and compared to those obtained by a numerical simulation.     

Novel InAs/(Al,Ga)Sb FET with direct gate-to-channel contact

A new type of FET has been fabricated in which the gate is in direct contact with the channel. There is no intervening charge separating layer. Instead, the separation of gate and channel carriers is achieved by using the staggered band alignment of InAs/(Al,Ga)Sb such that a p⁺ (Al,Ga)Sb gate layer is placed in direct contact with the n-type InAs channel. At 77 K the measured devices show both current gain and voltage gain, and a maximum transconductance of 500 mS/mm has been observed