H Vonk

Interfacet surface diffusion in selective area epitaxy of III–V semiconductors

In this letter, we discuss the interfacet diffusion of group-III species from {111} B facets to the (100) plane in planar selective area epitaxy. In general, this leads to enhanced vertical growth at the edges of the (100) surface. From such edge profiles, several groups have extracted adatom “diffusion lengths” of ∼1 μm. This is a factor of 100 larger than reported diffusion lengths obtained by reflective high energy electron diffraction, scanning tunneling microscopy, or growth-rate analysis. We show that these values are severely overestimated and that edge profiles only give information on the propagation velocity of macrosteps.

Multi Wavelength Lasers fabricated using Selective Area Chemical Beam Epitaxy

Fabrication of complex Photonic Integrated Circuits (PICs) requires the integration of Semiconductor Optical Amplifiers (SOAs) and Passive Waveguide Devices (PWDs) on a single substrate.

Interface manipulation in GaxIn1-xAs/InP multiple layer structures grown by chemical beam epitaxy

In this study the control of interfacial layers in nanometre thin heterostructures is demonstrated by variation of the growth interruption sequence (GIS) at the binary - ternary interfaces. All samples have been prepared by chemical beam epitaxy simultaneously growing the structures on exact (100) substrates and (100) substrates misoriented by towards (110). Characterization was by means of photoluminescence (PL) spectroscopy and high-resolution x-ray diffraction. It is shown that both composition and thickness of the interfacial layers can be manipulated on the (sub)monolayer scale with GIS times of the order of seconds. According to analysis of the x-ray data, interfaces can be tuned from compression to tension around nominally lattice-matched quantum wells of six monolayers thick. The PL investigations show that the tensile interfaces have no effect on the position of the PL peak maximum whereas compressive, InAs-like interfaces shift the transition to lower energy. This trend can be qualitatively understood but for all samples the calculated transition energies are higher than the measured values. Recommendations are given for further work which is not only of importance to the system but should be applicable to quantum well structures in other materials where heterojunctions involve changes in both the group V and group III sublattices.

Investigations on indium phosphide grown by chemical beam epitaxy

In this paper, we present a systematic study of the properties of indium phosphide (InP) layers grown by chemical beam epitaxy (CBE). Trimethylindium (TMIn) and phosphine (PH3) are used as source materials. The relation between the phosphine cracker temperature and the cracking efficiency has been studied by mass spectroscopy during growth. The growth rate and morphology of the layers have been studied by varying the TMIn and phosphine flow rates as well as the substrate temperature. We have found that, under a wide range of growth conditions, the deposition rate is only determined by and proportional to the TMIn flow rate. This is in agreement with literature. Additionally, we observe that the growth rate decreases below a certain phosphine to TMIn flow rate (V/III) ratio and becomes phosphine flow limited. From investigations of the growth rate as a function of temperature, it is concluded that the desorption of indium species from InP starts at a temperature slightly below 540°C. For this desorption process, we have found an activation energy of (217 ± 20) kJ/mol. Further characterization of the InP layers has been carried out by photoluminescence and Hall measurements. From both methods, the optimum growth conditions have been established. Under these conditions, we reproduc-ibly obtain InP layers showing linewidths of the donor-bound exciton transition at 5K around 0.25 meV and a mobility at 77K of about 7.0·104 cm2/Vs. From the analysis of the mobility in the temperature range from 20 to 300K, we conclude that, additionally to shallow donors and acceptors, deep-donor centers with an activation energy of about 150 meV are present in all layers.

A modified BCF model to quantitatively describe the (1 0 0)InP growth rate in chemical beam epitaxy

The growth rate and the diffusion length are crucial parameters from the viewpoint of both growth kinetics and applications, notably in the emerging field of selective area epitaxy. We have found that the vertical (1 0 0) growth rate of InP grown by CBE depends not only on group III flux and temperature, but also on the substrate misorientation angle. It decreases by a few percent for lower misorientations and the effect becomes more pronounced at higher temperatures. This is due to an increased probability for desorption of the group III adatoms. To quantitatively describe this growth rate dependence we developed a model based on classical crystal growth theories for step flow (BCF) and 2D nucleation. Using only two free parameters. we obtain an excellent fit to the experimental data. We find a value of E d - E s of 0.47 ± 0.01 eV, corresponding to a diffusion length of 13 nm at 515 C. and. for the first time, the energy barrier for the formation of a critical 2D nucleus. ΔG * , with values between 52 and 34 meV for growth rates from 0.3 to 0.6 μm.

Surface morphology of InP/GaInAs in selective area growth by chemical beam epitaxy

In this work some aspects of embedded SAE by chemical beam epitaxy are shown. The anisotropy in growth behaviour between 0° and off-oriented substrates is discussed in terms of the chemical difference between A- and B-type steps. The presence of B steps is beneficial for the InP morphology; simultaneous presence of A steps gives rise to (110) facets, which lead to macro-step formation. From a B step up edge no new B steps are generated during growth, causing a macroscopic ripple pattern starting from this edge. The terrace lengths of these ripples are sensitive to growth conditions that influence surface mobility. Furthermore, the surface diffusion is clearly anisotropic with fast diffusion along [011]. The morphological features can be explained by assuming a (2 × 4) reconstruction during growth.

Substitution of InP layers to InAs for strain compensation in GaxLn1-xAs/InP superlattices

Abstract In this study controlled substitution of P by As atoms, by exposing an InP surface to cracked arsine, is demonstrated to form thin InAs layers. All structures have been grown by chemical beam epitaxy. The effect of the exposure time has been investigated in InAs single and multiple quantum wells. Characterisation was performed by X-ray diffraction and photoluminescence spectroscopy. A two-stage substitution process is concluded. During the fast first stage the top P layer is exchanged by As. Longer exposure times lead to the complete substitution of the P layer underneath. In the mean time a three-dimensional rearrangement results in the formation of InAs islands. These thin compressed InAs layers have successfully been used for strain compensation in Ga x In 1 − x As InP superlattice structures.

Growth of GaxIn1−xAs/InP thin layer structures by chemical beam epitaxy

Abstract Multiple layer structures of InP and Ga x In 1− x As have been grown on InP substrates by chemical beam epitaxy (CBE). The samples were analyzed by photoluminescence (PL) spectroscopy at 5 K, double-crystal X-ray diffraction (DCXRD) and transmission electron microscopy (TEM). From 2000 A thick layers, the PL measurements revealed the variation of the composition as a function of growth temperature. The influence of the growth interruption sequence (GIS) on the interfacial layers of 10-period superlattices with a 20 A Ga 0.47 In 0.53 As well and a 40 A InP barrier is investigated. The time responsible for the exchange of P by As atoms at the “lower” ( InP → Ga 0.47 In 0.53 As ) interface is varied from 0 to 10 s at a growth temperature of 525°C. A minimal PL linewidth was observed for 1 s. TEM analysis showed abrupt transitions and a period thickness of 61 ± 3 A. Both simulation of DCXRD measurements and calculation of PL transition energies revealed the formation of minimally 1 ML InAs y P 1− y during the substitution at the “lower” interface.

HETEROGENEOUS HYDRIDE PYROLYSIS IN A CHEMICAL BEAM EPITAXY CRACKER CELL AND GROWTH OF HIGH QUALITY INP

The decomposition of phosphine and arsine in a chemical beam epitaxy cracker cell was investigated with a quadrupole mass spectrometer. We have determined the kinetical parameters for a unimolecular reaction of the first order, i.e. the activation energy and frequency factor, from the decomposition efficiency as a function of temperature. These results are compared with data from literature. We find the lowest activation energies ever reported for the hydride pyrolysis, namely 72 and 48 kJ/mol for phosphine and arsine, respectively. This is due to the heterogeneous decomposition on catalytic molybdenum baffles inside the cracker cell. Additionally, we have studied the impurity incorporation in epitaxially grown bulk InP layers in relation to the efficiency of this particular molybdenum containing cracker cell. Impurity levels were determined by fitting calculated Hall values to experimental data. The best quality is achieved for the cracker temperature at which the efficiency starts to saturate. At this c...

Effects of tensile strain and substrate off-orientation on the growth of GaInAsInP multiple quantum well structures by CBE

Abstract GaInAs InP multiple quantum well (MQW) layers with high tensile strain in the GaInAs layers have been grown by chemical beam epitaxy (CBE). The samples were analysed by high-resolution X-ray diffraction (XRD), photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM). The influence on layer properties of the tensile strain and the substrate off-orientation of the (100) InP substrates is investigated. XRD studies reveal that the growth rate of GaInAs as well as that of InP is larger for off-oriented substrates than for exactly oriented substrates. This behaviour is independent of the strain in the GaInAs layers and of the growth temperature in the chosen range between 485°C and 545°C. We attribute the observed changes of the growth rate to the different growth modes on exact (100) and off-oriented substrates. MQW structures grown on off-oriented substrates show a linear increase of the PL line width of the GaInAs MQW peak with increasing tensile strain in the GaInAs layers. In contrast, it stays constant for exactly oriented substrates. This increase in the PL line width for off-oriented substrates is explained by the lattice tilting occurring when strained layers are deposited on stepped surfaces. The tilt angle is proportional to the amount of incorporated elastic strain as shown by the azimuthal dependence of the position of the zeroth-order satellite reflection in XRD.