In1-xGaxAsyP1-y/InP DH lasers fabricated on InP

In1-xGaxAsyP1-y/InP double heterostructure (DH) laser diodes with emission wavelengths of1.25-1.35mum at room temperature were fabricated on     

LPE and VPE In1-xGaxAsyP1-y/InP: Transport properties, defects, and device considerations

The electrical properties of In1-xGaxAsyP1-yalloys lattice matched to InP, grown by liquid-phase and vapor-phase epitaxial techniques, have been determined by various measurements. Several electron and hole traps, with activation energies varying from 0.26 to 0.82 eV, have been identified by transient capacitance and photocapacitance measurements and their density and capture cross section have been measured. The 0.82 electron trap has emission and capture properties identical to the dominant 0.83 eV electron trap present in bulk and VPE GaAs. Hall measurements were made on the alloys in the temperature range of 20-600 K. Analysis of the mobility data has yielded the values of several transport parameters including the alloy scattering potentialDelta Uas a function of composition. The maximum value ofDelta U simeq 0.8eV corresponding to the bandgapE_{g} simeq 0.95eV. Photo-Hall measurements at low temperatures show the presence of donor- and acceptor-like defects in the LPE and VPE alloys, respectively. These centers exhibit persistent photoconductivity at low temperatures and have a high barrier energy (∼0.2 eV) associated with electron capture. Defects, which are possibly located in the interconduction-valley region, have been identified from analysis of Hall data forT > 400K. The strong temperature dependence of the threshold current in injection lasers and the large leakage currents near breakdown in avalanche photodiodes have been discussed in the fight of the defects identified in the present investigation.     

A study of the compositional transition layer in In1-xGaxAsyP1-yinP heterojunction interface

The atomic concentration of each composition of a thin quaternary layer grown by the two-phase supercooling LPE does not vary with the depth. The atomic concentration in the compositional transition layer versus the depth can be formulated as a hyperbolic tangent function which fits the experimental data very well.     

InP-In1-xGaxAsyP1-yembedded mesa stripe lasers

A laser structure was fabricated using two-step liquid-phase epitaxy, employing the melt-back technique. The fabrication and properties of this structure are described in detail. Good linearity of the power output up to power levels of 20 mW was obtained. The threshold current density at 300 K is 9-12 kA/cm². This high value is mainly due to Zn-diffusion from the third to the buffer layer during the second growth step of the fabrication process. The external differential quantum efficiency is 30-35 percent under pulsed operation at 25°C. The pulsed threshold current has an exponential behavior with temperature whereT_{0} = 60degC. The far-field beam divergences in the directions parallel and perpendicular to the junction plane are12-15degand35-40deg, respectively. Transverse mode stabilization was improved with this laser structure.     

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.     

10 000-h continuous CW operation of In1-xGaxAsyP1-yInP DH lasers at room temperature

Life tests of In1-xGaxAsyP1-y/InP DH lasers fabricated from     

GaxIn1-xAsyP1-y/InP injection laser partially loaded with first-order distributed Bragg reflector

GaInAsP/InP distributed Bragg reflector (DBR) lasers with a first-order grating were demonstrated experimentally for the first time at a wavelength of 1.3 μm. Single longitudinal mode oscillation was obtained at low temperature, and the temperature dependence of the lasing wavelength was 0.7-0.8 Å/deg. The equivalent refractive index of GaInAsP at the lasing wavelength of 1.3 μm was 3.50 at 186 K.     

Yellow—Green In1-xGaxP and In1-xGaxP1-zAszLED's and electron-beam-pumped lasers prepared by LPE and VPE

In1-xGAxPx(x= 0.6-0.7) and In1-xGaxAszP1-z(x= 0.7- 0.8 andz= 0-0.2) epitaxial structures for visible LED's and electron-beam-pumped lasers have been fabricated both by vapor-phase epitaxy (VPE) and by liquid-phase epitaxy (LPE). The crystal perfection and luminescent properties of layers grown on     

Au/Ge/Ni ohmic contacts to n-Type InP

The relationship between the electrical properties and microstructure for annealed Au/Ge/Ni contacts to n-type InP, with an initial doping level of 10¹⁷ cm^-3, have been studied. Metal layers were deposited by electron beam evaporation in the following sequence: 25 nm Ni, 50 nm Ge, and 40 nm Au. Annealing was done in a nitrogen atmosphere at 250-400‡C. The onset of ohmic behavior at 325‡C corresponded to the decomposition of a ternary Ni-In-P phase at the InP surface and the subsequent formation of Ni₂P plus Au₁₀In₃, producing a lower barrier height at the InP interface. This reaction was driven by the inward diffusion of Au and outward diffusion of In. Further annealing, up to 400‡C, resulted in a decrease in contact resistance, which corresponded to the formation of NiP and Au₉ln₄ from Ni₂P and Au₁₀In₃,respectively, with some Ge doping of InP also likely. A minimum contact resistance of 10^-7 Ω-cm² was achieved with a 10 s anneal at 400‡C.     

Continuous room-temperature photopumped laser operation of visible-spectrum LPE In1-xGaxP1-zAsz(λ ~ 6700 Å)

A modified version of the standard step cooled LPE growth process is described for the growth of visible-spectrum In1-xGaxP1-zAszdouble-heterostructure (DH) lasers on GaAs1-yPy(y sim 0.30). The quality of the quaternary epitaxial layers is improved by growing a "thick" uniform active region (∼1000 Å) by means of a multiple-layer stack of "thin" (∼100 Å) layers. Each of the "thin" layers grown (cyclically) from an equilibrium melt in the short growth period of <100 ms does not make a transition to the diffusion-limited conditions employed in standard LPE growth processes. This method of liquid-phase epitaxy has been used to grow In1-xGaxP1-zAsz-In1-x'Gax'- P1-z'Asz'(x sim 0.87, z sim 0.44; x' sim 0.66, z' lsim 0.01) DH's that operate as photopumped CW 300 K lasers atlambda sim 6700Å.     

Pd/Zn/Pd/Au ohmic contacts to ρ-Type InP

Low resistance ohmic contacts (ρ_c = 7 x 10^-5 Ω-cm ² ) have been fabricated to Zn-doped p-type InP using an annealed Pd/Zn/Pd/Au metallization. Palladium reacts with InP at low temperatures to form a Pd₂InP ternary phase, which is initially amorphous but crystallizes and grows epitaxially on InP. Zinc reacts with some of the overlying Pd to form PdZn (≅250° C), which decomposes at 400-425° C to form PdP₂, freeing up Zn to diffuse into Au as well as InP. The contact resistance reaches a minimum as the decomposition reaction takes place. The resultant ohmic contact is laterally uniform and consists of epitaxial Pd₂InP adjacent to InP, followed by a thin layer of PdP₂ and then the outer Au layer. Further annealing leads to a breakdown of the contact structure,i.e. decomposition of Pd₂InP, and an increase in contact resistance.     

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.     

Performance of InxGa1-xAsyP1-yphotodiodes with dark current limited by diffusion, generation recombination, and tunneling

We present a theoretical study of the effects of diffusion, generation-recombination (GR), and the recently observed tunneling currents on the performance of photodiodes made from In0.73Ga0.27As0.63P0.37and In0.53Ga0.47As. Calculations are made for both p+ν and p-i-n punch-through diode configurations, and are compared with recent measurements made by several independent investigators. For doping densities typical of present material (N_{D} gsim 10^{15}cm^-3), tunneling currents become dominant prior to avalanche breakdown. Thus, for detection of weak (-55 dBm at 45 Mbits/s) optical signals, the diodes must be operated at low voltages where GR is the dominant source of reverse-biased leakage. To meet the requirements of low capacitance (C leq 0.5pF for a diode area of 10^-4cm²) and low GR dominated dark current (I_{D} leq 10nA atT = 70degC), the doping density and effective carrier lifetime (τeff) must beN_{D} < 7 times 10^{15}cm^-3andtau_{eff} gsim 150ns for In0.73Ga0.27As0.63P0.37and5 times 10^{14} lsim N_{D} lsim 7 times 10^{15}cm^-3andtau_{eff} gsim 3.5 mus for In0.53Ga0.47As.     

Low resistance ohmic contacts to p-Ge1-xCx onSi

We report on ohmic contact measurements of Al, Au, and W metallizations to p-type epitaxial Ge_0.9983C_0.0017 grown on a (100) Si substrate by molecular beam epitaxy (MBE). Contacts were annealed at various temperatures, and values of specific contact resistance have been achieved which range from 10^-5Ω·cm² to as low as 5.6×10 ^-6Ω·cm². Theoretical calculations of the contact resistance of metals on Ge_1-xC_x with small percentages of carbon, based on the thermionic field emission mechanism of conduction, result in good agreement with the experimental data. We conclude that Al and Au are suitable ohmic contacts to p-Ge_0.9983C_0.0017 alloys     

Au/Ge/Pd ohmic contacts to n-GaAs with the Mo/Ti diffusion barrier

The influences of the As-outdiffusion and Au-indiffusion on the performances of the Au/Ge/Pd/n-GaAs ohmic metallization systems are clarified by investigating three different types of barrier metal structures Au/Ge/Pd/GaAs, Au/Ti/Ge/Pd/ GaAs, and Au/Mo/Ti/Ge/Pd/GaAs. The results indicate that As-outdiffusion leads to higher specific contact resistivity, whereas Au-indiffusion contributes to the turnaround of the contact resistivity at even higher annealing temperature. For Au/Mo/Ti/Ge/Pd/n-GaAs samples, they exhibit the smoothest surface and the lowest specific contact resistivity with the widest available annealing temperature range. Moreover, Auger electron spectroscopy depth profiles show that the existing Ti oxide for the Mo/Ti bilayer can very effectively retard Au-indiffusion, reflecting the onset of the turnaround point at much higher annealing temperature.