G.-P. Tang

Effect of III/V-Compound Epitaxy on Si Metal-Oxide-Semiconductor Circuits

Several approaches to the heteroepitaxial growth of InP on (100)Si employing an electrochemically etched Si mesa, SiO2 masks, and a maskless procedure were investigated with the objective of achieving area-selective InP integration into Si metal-oxide-semiconductor (Si-MOS) technology. Maskless InP/Si device layer growth by metal-organic vapour-phase epitaxy with good selectivity on a structured InP buffer layer, surrounded by oxide, was achieved. Undesired InP depositions were removed with an SiO2 emulsion, spun on prior to InP growth. To study the effects on the Si-based electronics, p-metal-oxide-semiconductor field-effect tansistors (MOSFETs) were exposed to the various stages of the heteroepitaxial InP growth process. We have studied the influence of hydride atmospheres and thermal anneals on their electrical performance. A standard InP-on-(100)Si growth procedure was found to be acceptable for the MOS components, as demonstrated by a Schmitt-trigger laser-diode driver circuit.

Antiphase-domain-free InP on (100) Si

We show that antiphase-domain-free InP can be grown by means of low-pressure metalorganic-vapor-phase epitaxy (LP-MOVPE) on exactly (100)-oriented Si by appropriate choice of growth parameters. A simple detection scheme for antiphase domains (APD) in InP is presented. The most likely reason for the absence of APDs on the InP surface is their annihilation during the growth.

Scattering mechanisms and defects in InP epitaxially grown on (001) Si substrates

Carrier concentration and mobility of unintentionally doped InP layers, grown directly on Si using metal‐organic vapor‐phase epitaxy, have been studied. The formation of antiphase domains (APDs) was found to depend on annealing of the Si substrate in an AsH3 flow prior to epitaxial growth. Dislocation densities determined by the wet chemical delineation technique were (8±1)×107 cm−3, seemingly uncorrelated to APDs in the layers. In addition to a shallow donor and a compensating acceptor, a deep donor was observed affecting the temperature dependence of the free‐electron concentration between 77 and 300 K. The electron mobility in this temperature range could be described in terms of the scattering mechanisms which are dominant in homoepitaxial InP, namely, scattering due to polar optical phonons, to ionized impurities, and to space charges. Electron scattering due to either of these mechanisms was strongly influenced by the occurrence of antiphase boundaries (APBs). The space‐charge density as well as the...

A new maskless selective-growth process for InP on (100) Si

We have developed a new selective‐growth process of InP on exactly (100)‐oriented Si substrate in a conventional low‐pressure metal‐organic vapor‐phase‐epitaxy system. In this process, the InP epitaxial layer was deposited on a photolithographically patterned InP‐buffer film without an additional dielectric mask during the growth. Under our experimental conditions, the InP growth has a very high selectivity and the InP epitaxial layer is antiphase‐domain free. Experimental results show that the undesirable sidewall‐growth interaction in conventional dielectric mask selective‐growth processes is effectively suppressed. Spatially resolved photoluminescence displayed very high optical quality of patterned InP layers compared to those grown on blanket substrates.

Performance of InGaAs metal-semiconductor-metal photodetectors on Si

The performance of In/sub 0.53/Ga/sub 0.47/As metal-semiconductor-metal photodetectors on Si substrates was investigated. The devices were fabricated by standard technology employing metalorganic vapor-phase epitaxy growth on unpatterned exactly [001]-oriented Si substrates and conventional photolithography. At a bias voltage of 5 V the devices exhibit low dark currents of 10/sup -6/-10/sup -7/ A, a high responsivity of 0.26 A/W at 1.3 /spl mu/m, and a cutoff frequency of 1.5 GHz. A further improvement could be achieved by increasing the bias voltage.

High-quality In0.53Ga0.47As on exactly (001)-oriented Si grown by metal-organic vapour-phase epitaxy

Abstract In this paper we report on results of an optimized growth process of In0.53Ga0.47As on exactly (001)-oriented Si substrates by low-pressure metal-organic vapour-phase epitaxy (LP-MOVPE). The crystalline perfection of the InGaAs as well as an intermediate layer sequence consisting of GaAs, InP and an InGaAs InP superlattice was examined by transmission electron microscopy, X-ray diffractometry, and dislocation etching. Electrical and optical characterization were performed using electrochemical capacitance-voltage profiling and photoluminescence spectroscopy. The InGaAs layer exhibits a lattice mismatch of 1 × 10−3 to InP, an etch-pit density of 1.3 × 108 cm−2, full widths at half maximum of 210 arcsec of the (004) X-ray reflex and of 15 meV of the excitonic photoluminescence peak at 2 K as well as a background doping concentration of 4 × 1016 cm−3. Using this layer high-performance photodetectors for the long-wavelength range were fabricated.

Dark-current analysis of InGaAs-MSM-photodetectors on silicon substrates

The fabrication process of InGaAs metal-semiconductor-metal (MSM) photodetectors on lattice-mismatched (001)Si substrates is described. The Schottky-barrier is enhanced by a p+n-InP double layer. The dark-current densities measured are comparable to those of lattice-matched devices on InP. Their distribution shows the good reproducibility of the fabrication process. From the temperature and voltage dependence of the dark current we find that on Si the current in the medium voltage range is noticeably influenced by tunneling which we relate to defect centres in the bandgap. Nevertheless, the dark current is low enough for applications of the MSM-detectors in optoelectronic systems.

Photoreflectance Study on the Effect of Lattice Defects in InP on (001) Si

The residual stress in epitaxial InP on (001) Si was investigated by photoreflectance spectroscopy. Depending on doping concentration, low-field and intermediate-field spectra were measured which were quantitatively analysed by a third-derivative approximation or by a multilayer model, respectively. In both cases, transitions only from the heavy-hole and the split-off valence subbands into the conduction band contributed to the spectra, while the light-hole to conduction-band transition was absent. In addition to the energy shift due to tensile strain caused by the different thermal expansion coefficients of InP and Si, a signal component originating from compressive strain in the InP was observed. This effect is attributed to the clustering of dislocations at twin defects. As a result, a model of the defect distribution in the heteroepitaxial InP layers was presented.

The influence of a hydride preflow on the crystalline quality of InP grown on exactly oriented (100)Si

Several microns thick epitaxial InP films have been successfully deposited on exactly oriented (100) Si substrates by metal-organic vapour-phase epitaxy. We have studied the influence of a hydride preflow before buffer growth on the crystalline quality of the InP by measuring the surface roughness, by X-ray diffractometry, TEM and SEM investigations, and by detection of anti-phase-domains. Generally, an AsH3 preflow instead of PH3 improved the crystalline perfection considerably. Furthermore, if AsH3 is introduced only during cool-down between 700 and 900° C after the thermal cleaning step anti-phase-domain free InP is grown.

Characterization of thin buffer layers for strongly mismatched heteroepitaxy

Thin buffer layers for strongly mismatched heteroepitaxy of GaAs and InP on Si were investigated with respect to their structural characteristics in a scanning electron microscope (SEM). A novel technique, which is based on energy-dispersive X-ray spectrometry (EDX), was utilized for thickness measurement. With GaAs thicknesses were determined in the range from several μm down to 10 nm. Their accuracy was confirmed by mechanical surface tracing of selectively etched steps. The crystal quality of the thin layers was probed by electron-channelling patterns (ECP). We found a dependence on buffer-layer thicknesses which was confirmed by spectroscopic ellipsometry. For thin layers the optical absorption coefficient near the band edge, which is a measure of the density of structural defects in thin layers, showed the smallest deviation from the bulk standard. Furthermore, the buffer-layer quality determined by ECP was correlated with the surface morphology and with the density of twin defects in subsequently grown thick main layers of GaAs and InP, respectively. We conclude that EDX and ECP are powerful methods for the structural characterization of thin buffer layers playing a key role in mismatched heteroepitaxy. Both techniques were performed in a SEM, which is a standard tool in research and development as well as in industrial laboratories.