Application of O+implantation in inverted InGaAs/InAlAs heterojunction bipolar transistors

Deep O+ implantation has been used to create a high-resistivity layer buried beneath the Be+ -implanted extrinsic base-emitter junction region of In0.52Al0.48As/In0.53Ga0.47As inverted (emitter-down) heterojunction bipolar transistors (HBT's). The O+ -implanted layer remains highly resistive even after a rapid thermal annealing step at 700°C to activate the Be+ implants. With the O+ implantation, the forward current of the extrinsic base-emitter diode is significantly reduced. HBT's with Be+ - and O+ -implanted extrinsic base regions exhibit current gains of ≃ 100 at a collector current density in excess of 10³A/cm². Another benefit from the deep O+ -implanted layer is a dramatic reduction in the junction capacitance of the extrinsic base-emitter diode.     

Growth and characterization of MO/VPE double-heterojunction lasers

Metalorganic vapor-phase epitaxy (MO/VPE) has been used for the growth and fabrication of double-heterojunction (DH) devices. Al0.3Ga0.7As/GaAs DH mesa stripe lasers were made, which have a threshold current density of 6.7 kA/cm². We attribute this high value to recombination losses at killer centers situated in the confinement layers very close to the active layer; it is shown that these killers were introduced by using dopant concentrations beyond4 times 10^{17}cm^-3. The MO/VPE technique was also applied for burying mesa lasers. The threshold current density of an LPE mesa buried with monocrystalline (Al, Ga)As was 3.5 kA/cm²; i.e., 60 percent higher than its corresponding broad-area value. It is shown that in order to reduce the excess current, the recombination velocity at the VPE/LPE active-layer interfaces should be lowered; viz., to a value below the diffusion velocity of carriers towards these interfaces. The optical mode structure of the buried mesa (BM) lasers was stable up to a power output of 10 mW/facet.     

Scaled CMOS technology using SEG isolation and buried well process

An advanced bulk CMOS technology has been developed using the selective epitaxial growth (SEG) isolation technique and buried n-well process. CMOS devices are fabricated on a selective epitaxial layer, isolated by a thick SiO2insulator over the p⁺substrate. p-channel devices are designed on buried n-wells, formed by introducing a phosphorus ion implantation into the p⁺substrate before the epitaxial growth. The use of an SiO2sidewall and square side direction is effective for defect-free selective epitaxy. The epitaxial autodoping effect from the p⁺substrate and the buried layer is estimated to be within less than 1 µm. A 20-nm-thick gate oxide and 500-nm-thick phosphorus-doped polysilicon gate electrode are used for both channel devices. Submicrometer gate CMOS operation is confirmed using the SEG isolation technique. This isolation structure, combined with the buried well, shows large latchup immunity for scaled CMOS circuits.     

D_2~ 轰击隔离条形(GaAl)As/GaAs双异质结构激光器

在室温至600℃退火D_2~ 轰击过的GaAs单晶片,只要退火温度低于200℃,得到的电阻率可达(1～2)×10~8欧姆·厘米。用D_2~ 轰击(GaAl)As/GaAs双异质结构片,制成的隔离条形激光器,近场、光谱、频率响应及退火等特性都与H~ 轰击激光器差不多。     

GaInAsP/InP DH lasers with a chemically etched facet

We describe a new configuration and novel fabrication method for GaInAsP/InP DH lasers in which one of the facet mirrors is chemically etched and the other one is formed by cleaving. The etched facet is fabricated monolithically by wet chemical etching in a solution of HCl:CH3COOH:H2O2= (1:2:1). Broad-area contact lasers of this type operating at room temperature at a wavelength ofsim 1.3 mum have been demonstrated.     

Substrate radiation losses in GaAs heterostructure lasers

Double-heterostructure (DH) diode lasers with a thin Ga1-xAlxAs layer between the active GaAs region and the GaAs substrate or superstrate are analyzed. In these devices power flows through the thin Ga1-xAlxAs layer and is radiated into the substrate or superstrate. Three methods for computing the laser thresholds are developed and compared. The first is an analytic perturbation technique, which yields accurate results in many cases of practical interest. The second and third are rapidly convergent numerical iteration techniques. The former utilizes overlap integrals to compute absorption losses and thresholds; the latter includes all losses and gains directly in the formulation. We show that conventional DH diode lasers can be designed with thick active GaAs layers and still achieve lowest order TE-mode operation. These devices will produce better collimated, higher power output beams than do similar devices with thinner active regions. Transverse-mode control is achieved because all higher order modes have increased penetration through the thin Ga1-xAlxAs , and therefore exhibit inereased radiation losses into the substrate or superstrate. A design example is included in which it is shown that with proper choice of the Ga1-xAlxAs-layer thickness the TE0-mode threshold increases by 5 percent compared with a 110-percent increase in the TE1threshold. These results are virtually independent of the substrate power-absorption coefficient. Threshold current densities are computed for a set of diodes studied experimentally by Casey and Panish and the results are shown to be in excellent agreement.     

A two-dimensional analysis for MOSFET's fabricated on buried SiO2layer

An accurate numerical analysis for predicting characteristics of MOSFET's Fabricated on an epitaxial Si layer on top of a buried SiO2layer formed by oxygen ion implantation is presented. Basic equations, that is, the current continuity equation for minority carriers, Poisson's equation, and the equation for the majority-carrier concentration including carrier multiplication due to impact ionization, are iteratively calculated for obtaining a self-consistent solution. Good agreement between theoretical and experimental results was obtained over a wide range of device parameters and terminal biases. Threshold dependence upon Si/buried SiO2interface charge as well as Si film thickness is shown. As the Si film and buried SiO2thicknesses are reduced, the threshold voltage shift with channel shortening becomes smaller. Finally, theoretical analysis shows that the short-channel effect in MOSFET fabricated on an epitaxial layer with an underlining buried SiO2layer is smaller than those in bulk Si MOSFET and MOSFET/SOS.     

Recombination enhanced annealing effect in AlGaAs/GaAs remote junction heterostructure lasers

New structure lasers, the remote junction heterostructure (RJH) lasers, are made to obtain information about slow degradation of AlGaAs/GaAs DH lasers. The RJH laser is characterized by the presence of a thin clad layer between the active layer and the p-n junction. During the LD and LED mode aging process, the RJH lasers showed a marked reduction of threshold current. This reduction was accompanied by increased spontaneous lifetime and pileup of defects at the p-n junction. From these observations, a model was proposed in which point defect generation in the active layer and defect motion toward the p-n junction during the aging are assumed. The rate equation was derived for concentration of the point defect, and the solution of this equation was compared with the experimental results with reasonable agreement. The parameters relating to the slow degradation were determined, and the ultimate life of conventional DH lasers was discussed using these parameters.     

Tapered windows in phosphorus-doped SiO2by ion implantation

Phosphorus-doped SiO2is frequently used as a dielectric coating in silicon integrated circuits. It is important that windows in this dielectric have sufficiently tapered walls so that the subsequent metallization has good step coverage. It is shown here that tapered windows can be made in both Nitrox-deposited ∼ 1-percent phosphorus-doped SiO2and Silox-deposited ∼ 7-percent phosphorus-doped SiO2as well as undoped SiO2by an ion implantation which produces a thin damaged layer at the top of the oxide. The damaged layer etches at a faster rate than the undamaged oxide. This fast-etching layer undercuts the photoresist which serves as the etching mask and results in window walls having slopes in the range of 30-40° with respect to the wafer surface. Tapering windows by ion implantation is a dependable process that gives reproducible results without having to rely on the art of photoresist liftoff methods.     

Temperature dependence of threshold current in (GaAl)as double-heterostructure lasers with emission wavelengths of 0.74-0.9µm

The threshold-current variation with temperature has been measured for Ga1-xAlxAs double-heterostructure (DH) lasers with AlAs mole fraction in the active layerxof 0.08 and 0.2, and with several heterojunction step heightsDeltax. The threshold-temperature coefficient Jth(350 K)/Jth(300 K), which generally increases with decreasingDeltax, is found to be larger forx = 0.2than that forx = 0.08at the same value ofDeltax, and also to be larger for the lasers with smaller effective electron diffusion length in thePcladding layer, in the case ofx = 0.2. These characteristics are well explained by a model of carrier leakage due to unconfined carriers in the active layer. It is confirmed by a good fit of the experimental results with the calculated values that the electron leakage in theGammaconduction band of thePcladding layer dominates forx leq 0.1, but the hole leakage in theNcladding layer increases withxand becomes comparable in magnitude with the electron leakage atx sim 0.2.     

Spectral linewidth and resonant frequency characteristics ofInGaAsP/InP multiquantum well lasers

The spectral linewidth and resonant frequency characteristics of 1.3-μm InGaAsP/InP multi-quantum-well lasers grown by liquid-phase epitaxy were investigated and compared to those of the conventional double heterostructure (DH) lasers. A decrease in spectral linewidth and an increase in resonant frequency f_r with decreasing well thickness were observed. Moreover, the linewidth enhancement factor α was reduced to ~2 for well thicknesses of less than ~200 Å, while that of the DH laser was ~6. An f_r of 9 GHz, which is twice as large as that of conventional DH lasers, was achieved at an optical power of 5.3 mW/facet     

Glass lasers

After a general discussion of the merits of glass vs. crystals as host materials for laser ions, a summary is given of the various glass lasers. Because of its importance as an efficient, room temperature laser the properties of neodymium are considered in greater detail. This includes the nonlaser properties of Nd³⁺in glass, the spectral and temporal emission characteristics of Nd³⁺lasers, and Nd³⁺laser configurations. Separate sections deal with the other two room temperature lasers which use Yb³⁺or Er³⁺. The problem of thermal of laser cavities is also discussed. Finally, a survey is given of the glasses that are useful as Faraday rotators.     

Single-mode operation of mushroom structure surface emitting lasers

Mushroom structure vertical cavity surface emitting lasers with a 0.6-μm GaAs active layer sandwiched by two Al_0.6Ga_0.4 As-Al_0.08Ga_0.92As multilayers as top and bottom mirrors are discussed. The lasers exhibit a 15-mA pulses threshold current at 880 nm. Single longitudinal and single transverse mode operation was achieved on lasers with a 5-μm-diameter active region of current levels near 2×l_th. The light output above threshold current was linearly polarized with a polarization ratio of 25:1     

GaInAs/AlGaInAs DH and MQW lasers with 1.5-1.7 mu m lasing wavelengths grown by atmospheric pressure MOVPE

The first successful growth and fabrication of long wavelength (1.5-1.7 mu m) DH and MQW lasers by atmospheric pressure MOVPE in a 'phosphorus-free' material system is reported. The GaInAs/AlGaInAs DH and MQW lasers were grown on InP substrates. DH lasers emitting at around 1690 nm exhibit threshold current densities down to 2.8 kA/cm/sup 2/ at 25 degrees C; the characteristic temperature is 50 K in the 15-55 degrees C range. First MQW lasers with 1565 nm emission wavelength have threshold current densities around 3.2 kA/cm/sup 2/.<>     

Three-layer 1.3 µm In1-xGaxAsyP1-ylasers with quaternary confining layers

Improvements in the surface morphology of InGaAsP DH wafers were obtained with addition of small amounts of Ga and As in the confining layers. This method was used to improve interface flatness between active and confining layers, consequently improving wafer yield and reproducibility. Three-dimensional lattice-mismatch data of the confining layers were determined in detail using simultaneous multiple Bragg diffraction of X-rays. In all wafers tested, independent of the active layer thickness, the maximum threshold current density Jthwas at most 60 percent higher than Jthminimum. The minimum normalized threshold current density obtained by us-3.4 kA/cm²μmis to our knowledge the lowest reported to date. Low resistance contacts-differential series resistance of 1 to 2 Ω for 10 μm SiO2stripe-geometry contact-can consistently be directly applied to tile top confining layer, thus dispensing with file need of a cap layer. CW operation at room temperature has been achieved with these three-layer devices.     

Near-infrared In1-xGaxP1-zAszdouble-heterojunction lasers: Constant-temperature LPE growth and operation in an external-grating cavity

InP-In1-xGaxP1-zAsz-InP (x sim 0.08, z sim 0.17) double-heterojuncfion (DH) lasers emitting atlambda sim 1.0 mum (77 K) have been fabricated by constant-temperature liquid-phase epitaxy (LPE). The crystal-growth process is described and compared to previous work on visible spectrum (lambda sim 6000-Å) In1-xGaxP1-zAszdouble-heterojunction lasers. Emission spectra are presented for the near-infrared quaternary DH lasers. In particular, the observation of cavity oscillations in the low-level spontaneous-emission spectra allows the determination of the index dispersion quantity over a wide wavelength range. Finally, these In1-xGaxP1-zAszDH lasers are operated in an external-grating cavity. Such operation permits tunable, narrow-linewidth laser emission and provides information concerning radiative-recombination processes. Comparisons are made to earlier work on external-grating operation of visible-spectrum (lambda sim 6000-Å) In1-xGaxP1-zAszDH lasers.     

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.     

Dielectric loss and current—Voltage measurements in sodium-contaminated Si—SiO2—Cr structures

A detailed study of the small-signal ac response of ntentionally sodium-contaminated Si-SiO2-Cr structures has been made with mobile ion concentrations of 10¹⁰-10¹²ions/cm², in the frequency range of 0.05-100 Hz, between temperatures of 300 and 450°C. The time dependence of the observed relaxation phenomena, attributed to the existence of deep traps near the SiO2-Cr interface, is slow enough to consider the measured relaxation spectra as quasi static. The dc bias dependence of the relaxation mechanism, manifested by a loss maximum around 0.6 V and by a monotonic decrease of the absorption frequency with increasing bias, is ascribed to shallow traps located at the SiO2-Cr interface. The trapping as well as the long range migration of Na⁺ions in SiO2has been carefully studied by I-V and C-V measurements carried out on both contaminated and on ultraclean samples. The long-range motion of the ions leads to the thickness dependence of the relaxation time. However, since the ac response is determined in the two halves of the measuring cycle alternately by the migration of ions in the bulk of the SiO2and by their emission from the shallow traps, the relaxation time is also dependent on the effect of the traps. Consequently, the observed bias-dependent activation energies, ranging from 0.91 to 1.21 eV, may also be interpreted as intermediate values, arising from the conduction of Na⁺ions in SiO2films with an activation energy of less than 0.91 eV, and from the release of ions from the traps having activation energies equal to or greater than 1.21 eV.     

1.3 μm InGaAs/GaAs strained quantum well lasers with InGaPcladding layer

Using MOVPE, we fabricated strained quantum well 1.3 μm lasers with an InGaP cladding layer on a GaAs substrate. The lasers had a high gain coefficient of 60 cm^-1. Lasers with high reflection facets had a low threshold current density of 500 A/cm², and a high characteristic temperature of 100 K