Short interval open tube diffusion of Zn in GaAs at low temperatures (original) (raw)
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Investigation of Zn diffusion by SIMS and its effects on the performance of AlGaInP-based red lasers
Semiconductor Science and Technology, 2006
The behaviour of Zn diffusion in a GaInP/(Al 0.5 Ga 0.5 ) 0.5 In 0.5 P multiple quantum-well (MQW) layer was investigated as a function of the growth temperature and Zn/III ratio by secondary ion mass spectroscopy (SIMS). Then the diffusion length of Zn in the undoped (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P layer from the Zn-doped (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P (Zn: 1.0-1.2 × 10 18 cm −3 ) cladding layer was evaluated to design a barrier layer for Zn diffusion into the GaInP/(Al 0.5 Ga 0.5 ) 0.5 In 0.5 P MQW active layer. As a result of incorporating a 130 nm thick diffusion barrier on top of the MQW layers of the AlGaInP red laser, the full width at half maximum (FWHM) of the photoluminescence (PL) spectrum for the GaInP/(Al 0.5 Ga 0.5 ) 0.5 In 0.5 P MQW layers was reduced from 60 meV to 30 meV at room temperature (RT), and the threshold current was also greatly reduced from 110 mA to 75 mA for a standard AlGaInP-based ridge laser as compared to a AlGaInP laser without a diffusion barrier.
Diffusion of Pt in molecular beam epitaxy grown ZnSe
Diffusion of platinum in zinc selenide has been studied by the use of the 4 He and 12 C ion backscattering techniques. The samples were thin films grown by molecular beam epitaxy on GaAs 100 epitaxial layers followed by evaporation of platinum and annealing in the temperature range 500–800 °C. The diffusion coefficients were determined by the fitting of a concentration independent solution of the diffusion equation to the experimental depth profiles. The activation energy and the pre-exponential factor of the diffusion process were found to be 1.7 eV and 6.4 10 6 cm 2 /s, respectively. Zinc selenide as a base for blue light emitting diodes and blue semiconductor lasers has gained increased attention in the last few years. In order to make these devices work it is of great importance to be able to construct a thermally stable ohmic contact to the semiconductor. These contacts are often heterostructures consisting of many different metals, for example Pt, Au, Ti and Ni, 1–4 and to improve the contact properties they often have to be annealed at temperatures up to 350 °C for 45 min. 5 It is thus of prime importance to know the thermal stability of such a metal/semiconductor hetero-structure. Previously some research has been done on the electrical properties of Pt/ZnSe heterostructures 1,6 and interfacial reactions. 7 Some of these studies report indiffusion of platinum and outdiffusion of zinc, but they do not, however, report any quantitative data of the diffusion of platinum in ZnSe. In this letter we report on the activation energy and pre-exponential factor for the diffusion of platinum in ZnSe. Unintentionally doped n-type ZnSe was grown on an epitaxial p-GaAs buffer layer. The growth temperature and the beam pressure ratio Se:Zn of the layers were 290 °C and 2:1, respectively. The thickness of the ZnSe layer was 1.9 m. At this thickness the layer structure was relaxed, due to lattice mismatch between GaAs and ZnSe. The lattice relaxation was confirmed by x-ray diffraction measurement for each sample. After growth the sample sets were immediately transferred to an e-beam vacuum evaporator chamber, where a 10 nm thick platinum layer was deposited onto one of the sample sets labeled I and a 100 nm thick platinum layer onto a second one labeled II. The two thicknesses of platinum were deposited on the ZnSe in order to study the effect of the metal film thickness on the diffusion properties.
Journal of Applied Physics, 1999
Enhancement of interdiffusion in GaAs/AlGaAs quantum wells due to anodic oxides was studied. Photoluminescence, transmission electron microscopy, and quantum well modeling were used to understand the effects of intermixing on the quantum well shape. Residual water in the oxide was found to increase the intermixing, though it was not the prime cause for intermixing. Injection of defects such as group III vacancies or interstitials was considered to be a driving force for the intermixing. Different current densities used in the experimental range to create anodic oxides had little effect on the intermixing.
Raman spectroscopic studies of ZnSe/GaAs interfaces
Journal of Raman Spectroscopy, 2008
ZnSe/semi-insulating GaAs interfaces were studied by observing photogenerated plasmon-LO (PPL) coupled modes by nonresonant micro-Raman spectroscopy. The effect of the carriers generated by the focused laser beam was investigated for a series of different thicknesses of ZnSe epitaxial layers. The PPL mode in GaAs was observed in the micro-Raman spectra for all samples, but with different magnitude. The plasma is believed to be an electron gas as a result of the negative nature of the interfacial region that contains predominantly hole traps. The free carrier concentration is estimated to be >10 18 cm −3 and their lifetime ∼0.1 ns. This relatively long lifetime suggests that the ZnSe/GaAs interface has to be of high structural quality leading to a low recombination velocity. ZnSe/GaAs heterostructures of less crystalline quality (as determined by resonant Raman measurements) shows the effect of photogenerated carriers only to lesser extent.
Low temperature photoluminescence properties of Zn-doped GaAs
Materials Science and Engineering: B, 1998
Dimethylzinc (DMZn) was used as a p-type dopant in GaAs grown by low pressure metalorganic chemical vapor deposition (MOCVD). The influence of growth parameters, such as, DMZn mole fractions, growth temperature, trimethylgallium (TMGa) mole fractions, substrate surfaces on the Zn incorporation have been studied. The surface morphology of the layers was measured by scanning electron microscopy (SEM). The hole concentrations and zinc (Zn) incorporation efficiency are studied by using Hall effect, electrochemical capacitance voltage (ECV) profiler, and low temperature photoluminescence (LTPL) spectroscopy as functions of hole concentration (10 17 −1.5×10 20 cm − 3 ) and experimental temperatures (4.2 -300 K). The hole concentration increases with increasing DMZn and TMGa mole fractions and decreases linearly with increasing growth temperature. The main PL peak shifted to lower energy and the full width at half maximum (FWHM) increased with increasing hole concentration. An empirical relation for FWHM, DEp, band gap, Eg, and band gap shrinkage, DEg in Zn doped GaAs as a function of hole concentration were obtained. These relations are considered a useful tool to determine the hole concentration in Zn doped GaAs by low temperature PL measurement. The hole concentration increases with increasing TMGa mole fraction and the main peak is shifted to lower energy side.
Performance improvement of 650nm band AlGaInP laser diodes with optimal diffusion barriers
Materials Science and Engineering: B, 2006
GaInP/AlGaInP multiple quantum-well (MQW) laser diodes with diffusion barriers for Zn, grown by metal organic chemical vapor deposition (MOCVD), were fabricated and characterized. To determine the optimal conditions for the diffusion barriers, we investigated Zn diffusion in the GaInP/(Al 0.5 Ga 0.5 ) 0.5 In 0.5 P MQW layers against three undoped (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P diffusion barriers with thicknesses of 0, 90, and 130 nm, respectively, by secondary ion mass spectroscopy (SIMS). Compared to the reference AlGaInP laser diode without a diffusion barrier, the AlGaInP ridge laser with a 130 nm thick diffusion barrier on the top of the MQW layer had a threshold current that was greatly reduced from 110 to 75 mA and the characteristic temperature T o that was increased from 113 to 144 K in the temperature range from 25 to 50 • C. This report presents quantitative information on the effect of Zn diffusion on laser performance.
IEEE Journal of Quantum Electronics, 2000
We present an experimental and theoretical investigation of the temperature dependence of the threshold current for double quantum well GaInNAs-GaAs lasers in the temperature range 10 C-110 C. Pulsed measurements of the threshold current have been performed on broad and narrow ridge wave guide (RWG) lasers. The narrow RWG lasers exhibit high characteristic temperatures ( 0 ) of 200 K up to a critical temperature ( ), above which 0 is reduced by approximately a factor of 2. The 0 -values for broad RWG lasers are significantly lower than those for the narrow RWG lasers, with characteristic temperatures on the order of 100 (60) K below (above) . Numerical simulations, using a model that accounts for lateral diffusion effects, show good agreement with experimental data and reveal that a weakly temperature dependent lateral diffusion current dominates the threshold current for narrow RWG lasers.
Journal of Applied Physics, 1985
The vacuum metalorganic-chemical-vapor-deposition (Vacuum MOCVD) process was combined with two source purifications to grow p-GaAs epitaxial films of high quality. Theoretical modeling of quantum yield spectra measured on a specially configured n +-p sample determined the minority-carrier electron diffusion length to be 10 pm to within a factor of2 in the p layer. The p doping was reduced to the 5X 10 17 cm-3 level to avoid suppression of the diffusion length by Auger recombination. Multiple vacuum sublimations of dicycIopentadienyl magnesium (CP 2Mg), the source ofMg for p doping, reduced the contamination by air and by cyclopentadiene (CP) by an order of magnitude. A dry ice/acetone cold trap was operated at slightly below 180-Torr pressure to reduce the water vapor content of arsine, used as the As source, from the hundreds of ppm down level down to the 2 ppm range. The vacuum growth process reduced residual gas contamination. These techniques were combined to grow a p on n GaAs solar cell with an efficiency of 24% at air mass 1.5 (AM1.5).
Evaluation of the diffusion length of minority carriers in bulk GaAs
Applied Surface Science, 1991
The diffusion length of minority charge carriers has been investigated in LEC GaAs, silicon-doped with doping density ND - NA ranging from 10 16 to 10 18 cm -3, by surface photovoltage (SPV) and electron-beam-induced current (EBIC) of scanning electron microscopy (SEM) measurements. Au Schottky diodes have been evaporated along the diameter of wafers cut from different doping density ingots to determine the variation of minority carrier diffusion length with both the radial position on the slice and the carrier concentration. The diffusion length values obtained by optical and electron excitation enhance systematic differences, which can be explained by the different surface recombination weight in the carrier generation volume and by the injection level, too. In all the examined samples an M-shaped radial variation of the diffusion length has been observed; on the other hand, the mean value of Lp increases from 0.5 to 7 μm when the doping concentration increases. The authors correlate this distribution to the electrical inhomogeneity induced by native defects and associated recombination centres. The role of the dislocations, which induce two competitive effects, i.e. an enhanced recombination probability and a precipitate condensation, is here discussed.
Investigations of MOVPE growth of zinc delta doped GaAs
The Fifth International Conference on Advanced Semiconductor Devices and Microsystems, 2004. ASDAM 2004., 2004
This work presents the study of MOVPE growth of Zn-5-doped GaAs epilayers. A basic 5-doping procedure "purge-doping-purge" was applied The influence of the growth temperature, zinc concentration in gas phase and c5-doping lime on the density and spatial distribution oj holes was investigated The electrical and optical properties of the test structures were examined using Bio-Rad EC-V PN 4300 electrochemical capacitance-voltage profiler and photoreflectance spectroscopy PR.