MOVPE growth of (Al, Ga)InP-based laser structures monitored by real-time reflectance anisotropy spectroscopy

Using a specially-designed spectrometer enabling combined reflectance anisotropy spectroscopy (RAS) and reflectance measurements on rotating substrates in a commercial MOVPE reactor, we report the first full-spectroscopic RAS-monitoring of (Al,Ga)InP-based 650 nm laser growth. First, a spectral database was built up from systematic studies of AlGaInP RAS signatures for different Al compositions, doping levels and growth temperatures. These data are subsequently used for the interpretation of characteristic RAS fingerprints taken throughout the entire laser growth process. From the analysis of characteristic changes in the RAS spectra even small deviations from the optimum process (doping levels, composition, etc.) which would effect the performance of the final device can be detected.     

Coexistence properties of phase separation and CuPt-ordering in InGaAsP grown on GaAs substrates by organometallic vapor phase epitaxy

CuPt-ordering and phase separation were directly investigated in In_1-xGa_xAs_yP_1-y with a low arsenic content grown by organometallic vapor phase epitaxy on GaAs substrates. CuPt-ordering and phase separation in samples grown at the substrate temperatures of 630 and 690 °C were characterized by transmission electron diffraction and transmission electron microscopy. Although the immiscibility of InGaAsP was enhanced at the lower substrate temperature, the sample grown at 630 °C showed less phase separation than the 690 °C-grown sample. The degree of CuPt-ordering was significantly enhanced in the sample grown at 630 °C. The results demonstrated that the CuPt-ordering originating from surface reconstruction of P(2×4) suppressed the phase separation even in the miscibility gap. The detailed characterization of the phase separation clearly revealed a vertical composition modulation (VCM) in InGaAsP for the first time. The mechanism of the VCM formation is discussed based on the modulated-strain field on the surface.     

Study of GaAsBi MOVPE growth on (1 0 0) GaAs substrate under high Bi flow rate by high resolution X-ray diffraction

GaAsBi alloy was grown on (1 0 0) GaAs substrate by metalorganic vapour phase epitaxy. GaAsBi film was elaborated with V/III ratio of 9.5, trimethyl bismuth molar flow rate of about 3 μmol/min and a growth temperature of 420 °C. The surface morphology of GaAsBi alloy was investigated by means of scanning electron microscopy and atomic force microscopy. Results show surface Bi droplets formation. High-resolution X-ray diffraction (HRXRD) curves present more diffraction peaks other than that of GaAs substrate. Detailed HRXRD characterization shows that diffraction peaks splitting do not represent a crystallographic tilting with respect to GaAs substrate. Diffraction patterns also show a remarkable stability of the alloy against thermal annealing.     

In-situ monitoring of InP(100) and GaP(100) interfaces and characterization with RDS at 20 K

MOVPE-preparation of highly ordered InP(100) and GaP(100) surfaces was monitored with in-situ reflectance difference spectroscopy (RDS). Specific ordered P-terminated and ordered cation-terminated surface reconstructions were identified with specific structured RD spectra with the highest peaks. After contamination-free transfer of the samples to UHV, RDS measurements were performed also at 20 K. The experimental RD spectrum for the In-terminated, (2×4) reconstructed InP(100) surface shows a remarkable similarity to a recently published theoretical spectrum, whereas there is only moderate similarity between the experimental RD spectrum for the (2×4) reconstructed Ga-terminated GaP(100) surface and a recently proposed theoretical spectrum.     

InGaAsP multiple quantum well edge-emitting light-emitting diode showing low coherence characteristics using selective-area metalorganic vapor phase epitaxy

Low coherence multiple-quantum well edge-emitting light-emitting diodes were obtained using selective-area metalorganic vapor-phase epitaxial growth, which utilized growth rate enhancement on an open stripe region between mask stripes. An optical absorption region, which was controlled by selective-area growth, was introduced to suppress optical feedback. At a driving current of 100 mA and an ambient temperature of 25°C, a power of 55 μW was coupled into a single-mode fiber, and a broad spectrum without spectral ripple was observed. Low coherence characteristics and very small temperature dependence were obtained in the temperature range from -40°C to 85°C. The modulation bandwidth was 210 MHz at a bias current of 100 mA.     

Large scale production of indium antimonide film for position sensors in automobile engines

We use low pressure MOVPE to grow indium antimonide films on groups of eight 3 inch GaAs wafers per run. The films are used for the production of magnetoresistive position sensors for the car industry. To meet the narrow specifications for automotive components, the standard deviation of the sheet resistivity, and the thickness of the films have been reduced below 1.5%. This uniformity is the result of an optimization process encompassing the determination of the best susceptor temperature and the optimum flow. The gas velocity was found to have a large impact on the uniformity of the layers. Rotation of the wafers and the use of an optimum gas velocity results in extremely uniform layers.     

MOVPE生产用高纯水中硅的去除

本文介绍了硅对砷化镓材料生长及有机金属化合物气相淀积(MOVPE)工艺中的影响和电脱盐(EDI)技术以及用EDI降低高纯水中硅浓度的机理和方法,通过大量实验比较不同制水设备脱硅效果,得出用EDI技术严格控制pH(8~11)时脱硅效果最好,能使高纯水中Si的浓度＜0.5μg/L,满足了MO源生产及MOVPE工艺用水中Si浓度<3μg/L的需要.     

GaAs microlens arrays grown by shadow masked MOVPE

This paper describes the fabrication of high quality GaAs microlenses and microlens arrays using shadow masked metalorganic vapor phase epitaxial (MOVPE) growth (SMMG). Microlenses with apertures as small as 30 μm were fabricated and focal lengths down to 40 μm were measured. The smaller lenses closely fit the theoretical behavior of ideal spherical lenses while larger lenses (focal length >80 μm) showed a more complex physical shape and could not be modeled as spherical. This deviation from a spherical shape is expected from simulation of SMMG. The full width at half maximum of the beam waist was <2 μm for all sizes of microlens indicating that these lenses are compatible with coupling to single mode fibers.     

Optimal growth interrupts for very high quality InGaAs(P)/InP superlattices grown by MOVPE

The effects of different growth interrupt schemes at the compositional interfaces in 30 period InGaAs(P)/InP superlattices grown by metal-organic vapor phase epitaxy have been studied for quarternary compositions λ = 1.35 and 1.52 μm as well as for the ternary case λ = 1.67 μm. The best full width at half maximum of the photoluminescence peaks at 4 K are 7–8 meV for the InGaAsP/InP and 4.6 meV for the InGaAs/InP superlattices indicating extremely high optical quality and vertical homogenity of the samples. However, strong memory effects relating to both the presence and the absence of arsenic are evident from x-ray diffraction measurements. Reactor purging as a remedy is limited by the surface roughening and defect formation induced by a non-equilibrium vapor phase composition. Optimal growth interrupts must therefore be determined considering both the interface smoothness and abruptness and will in general be composition dependent.     

Automatic counting of etch Pits in InP

A computer algorithm for automatic EPD-counting (etch-pit density) with an optical microscope is presented. Several dislocation etchants proposed in the literature to reveal structural defects on InP were employed and improved. Their reliability for automatic counting was proven. For a considerable number of samples exhibiting an EPD between 10⁴ and 10⁶ cm⁻² it is shown that the automatically counted number of etch pits agrees with the visually determined value within less than ±30%. Using a modified H₃PO₄:HBr etchant good results for automatically determined EPDs beyond 10⁷ cm⁻² were obtained on InP layers epitaxially grown on Si substrates.