E. Veuhoff

Mg diffusion during metalorganic vapor phase epitaxy of InP

The diffusion mechanism of Mg has been studied during low‐pressure metalorganic vapor phase epitaxy of InP. The Mg dopant profiles were measured by secondary‐ion mass spectroscopy. The analysis reveals that abrupt Mg dopant profiles are possible; the Mg diffusion, however, strongly depends on the Mg concentration in the crystal lattice. Simultaneous doping with Si leads to a distinct decrease of the Mg diffusion. This behavior is consistent with a model assuming that Mg diffuses as a complex involving a deep donor.

Tunable twin-guide lasers with flat frequency modulation response by quantum confined Stark effect

For the first time results on the frequency modulation response of tunable twin‐guide laser diodes utilizing the quantum confined Stark effect in a multiquantum well modulation layer are presented. The structures were grown by metalorganic vapor phase epitaxy and were processed into ridge‐waveguide lasers emitting at 1555 nm. Preliminary devices exhibit single‐mode output power levels of more than 10 mW and minimum linewidths around 4 MHz. The frequency modulation response is flat up to 2 GHz with a modulation efficiency of 7 GHz/V.

Comparison of Zn and Mg incorporation in MOVPE InP/GaInAsP laser structures

The objective of this work is to study the incorporation process of Zn in InP and related ternary and quaternary layers for long wavelength laser applications in comparison with the alternative acceptor Mg. In InP above a critical concentration of (1–2)×1018 cm−3 a sudden onset of dopant diffusion during growth is observed for Zn and for Mg as well. This diffusion during growth can be markedly reduced by counter-doping with Si (Fermi level effect). Below the critical concentration Zn dopant profiles exhibit the same steep flanks as Mg dopant profiles suggesting the same low diffusion coefficients. However, Zn appears to be more suitable forp-type doping of InP, GaInAs and GaInAsP, because an accurate control of the dopant level in the epitaxial layers is easier to achieve with Zn than with Mg.

Potential of MOMBE/CBE for the production of photonic devices in comparison with MOVPE

Abstract Metalorganic molecular beam epitaxy (MOMBE/CBE), which has initially been introduced as a method for fundamental research, has become a growth technology for high quality device structures. The potential of this new technology as an industrial tool for the production of InP based photonic devices is discussed in comparison to metalorganic vapor phase epitaxy (MOVPE). Economical, ecological, yield and safety aspects show a significant advantage of MOMBE for industrial use. Furthermore, the unique MOMBE growth capabilities may open the path to the production of new device generations. Very high volume applications, however, will probably remain the domain of MOVPE. Thus the main industrial application of MOMBE will be in areas where an enabling technology for the production of sophisticated III–V device structures is required. In addition, MOMBE offers advantages, when environmental issues are of major concern, and when stringent safety and yield requirements have to be fulfilled.

Evaluation of III–V growth technologies for optoelectronic applications

Abstract In this review, the capabilities of molecular beam epitaxy (MBE), metalorganic vapour phase epitaxy (MOVPE) and metalorganic molecular beam epitaxy (MOMBE) or chemical beam epitaxy (CBE) for the growth of optoelectronic layered structures are evaluated, Both MBE and MOVPE are used in production of discrete devices and for future integration, MOMBE/CBE can play an increasing role due to unique features which include perfection in selective area epitaxy and environmental safety aspects. Moreover the combined multistage use of these growth technologies to generate new epitaxial device concepts offers very important potential. This is shown here by the example of a laser-amplifier/waveguide integration using MOVPE and MOMBE.

Electroabsorption in InGaAsP: electro‐optical modulators and bistable optical switches

We report Franz–Keldysh absorption spectra of InGaAsP obtained from transmission and photoresponse measurements in InP/InGaAsP/InP p‐i‐n double heterostructures. The values of the absorption changes (Δαmax≊3000 cm−1) are comparable with those obtained from the quantum‐confined Stark effect. Optical bistability is observed at very low light intensities (40 μW/cm−2), due to very low leakage currents and the strong absorption changes above the band gap.

Mg incorporation process during LP-MOVPE of InP, GaInAs and GaInAsP

Abstract The Mg incorporation process has been studied during low pressure metalorganic vapor phase epitaxy of InP, GaInAs and GaInAsP layers. In InP a cubic increase of the carrier concentration versus Mg flow in the gas phase is observed; a maximum carrier concentration of 2 × 10 18 cm −3 can be obtained. Results from Hall measurements and low temperature photoluminescence suggest that above a critical level of 10 18 atoms/cm 3 Mg is incorporated in InP both as a substitutional acceptor and as an interstitial donor. In ternary layers and in quaternary layers with a rather high Ga content the carrier concentration exhibits a square increase versus Mg flow; a saturation at a level of approximately 1 × 10 19 cm -3 is reached. The data can be explained assuming that in Ga containing compounds, such as ternary and quaternary layers, the concentration of interstitial Mg is much lower than in InP leading to a markedly reduced Mg diffusion during growth even at high concentrations.

Exploitation of surface selective growth in metalorganic growth technologies for device applications

Surface selective growth (SSG) is gaining importance for the realization of complex device concepts. This review article addresses basic SSG mechanisms both in metalorganic vapor phase epitaxy (MOVPE) and in metalorganic molecular beam epitaxy (MOMBE/CBE). It is described how these mechanisms can be exploited for the fabrication of complex devices focusing on the InP based material system. Additionally it is shown that with novel precursors new effects can be observed in SSG. The applications of SSG are highlighted by a discussion on selected devices. A critical comparison reveals that SSG in MOVPE can find some applications, but MOMBE offers higher flexibility, moreover a higher yield than in MOVPE can be expected. Therefore, MOMBE appears to be the preferred technology for SSG. However, since MOMBE is not established in production, a substantial R&D back-up is required for an industrial application of SSG in MOMBE.

GRINSCH GaInAsP MQW laser structures grown by MOMBE

For applications in long wavelength MQW lasers, GaInAsP/InP heterostructures were grown by metalorganic molecular beam epitaxy (MOMBE or CBE). The growth process was performed with all gaseous sources for group III, group V and dopant precursors. In addition to the standard strained MQW laser structure with two quaternary separate confinement layers on each side of the active MQW region, laser structures with continuously graded GaInAsP confinement layers (GRINSCH) were prepared. In the latter case all group III and group V flows were ramped synchronously while maintaining lattice matching growth conditions. By this method a parabolic variation of the band gap was obtained. Data from first test lasers are comparable to those from standard lasers revealing the high material quality of MOMBE grown InP-based GRINSCH structures. Besides standard strained quaternary layers InAsP layers with compressive strain up to 2% were used as quantum wells, and InAsP MQW lasers with emission wavelengths of both 1.3 and 1.55 μm were fabricated. Moreover, an excellent MQW wavelength uniformity (standard deviation Δλ ≤ 2 nm) across areas larger than 95% of a 2 wafer along with proven thermal stability demonstrates the high yield of the process for all structures revealing the feasibility of this material for industrial use.

Zn doping of InPGaInAsP device structures in metalorganic molecular beam epitaxy using diethylzinc

Diethylzinc was used as a gaseous p-type dopant source for growth of InP/GaInAsP layers in metalorganic molecular beam epitaxy. In InP layers a significant effect of growth temperature on Zn incorporation and on electrical activation has been found. Additionally, data from a variation of the dopant cracker cell temperature suggest that the dopant molecules should not be fully decomposed for an efficient dopant incorporation. A comparison of Hall data with data from secondary ion mass spectrometry (SIMS) reveals that in InP up to 60% of the acceptors appear to be electrically active under optimized experimental parameters, in GaInAs the activation is above 90%. The SIMS data show that dopant profiles with steep flanks can be obtained in InP/GaInAsP structures. However, a dopant redistribution occurs, which is more pronounced in InP layers. This effect is correlated with the dopant incorporation behaviour on substitutional and interstitial sites. The dopant incorporation process is discussed in detail, and the implications for growth of InP/GaInAsP device structures are outlined.