M.A. Koza

Patterned quantum well heterostructures grown by OMCVD on non-planar substrates: Applications to extremely narrow SQW lasers

Abstract We have studied the OMCVD growth of GaAs/AlGaAs quantum well heterostructures on non-planar substrates in the temperature range of 625 to 750°C. The lateral variation in layer thickness and other growth features were found to depend not only on the growth temperature but also on the aluminum content of the layer. An example of the application of this technique of producing lateral thickness variations in quantum well heterostructures to a quantum well semiconductor laser is given. A unique feature of this laser is the formation of a quantum-wire-like crescent shaped active region at the center of a two-dimensional optical waveguide.

Orientation dependence of S,Zn,Si,Te and Sn doping in OMCVD growth of InP and GaAs : application to DH lasers and lateral p-n junction arrays grown on non-planar substrates

Abstract The orientation dependence of doping in organometallic chemical vapor deposition (OMCVD) is shown to be far more complex than previously believed, with the variation of doping with increasing misorientation from (100) towards the (111)A/B being non-monotonic. However, the ratio of the n-doping on the B face to that on the corresponding A face is always greater than 1, irrespective of whether the dopant is a group IV or VI element. For p-doping with Zn, the reverse is true. The orientation dependence of doping has been used to create current blocking layers in InP/InGaAsP double heterostructure (DH) and multiple quantum well (MQW) lasers grown in a single step on a mesa or in a V-groove.

Growth of high‐quality GaAs using trimethylgallium and diethylarsine

In this letter we report the growth of high‐quality gallium arsenide using trimethylgallium and diethylarsine. The epitaxial layers had excellent morphology, an n‐type background free‐carrier concentration as low as 3×1014 cm−3 and a liquid nitrogen temperature mobility as high as 64 600 cm2/V s. The low‐temperature (2 K) photoluminescence spectrum has well‐resolved excitonic peaks, confirming the high quality of the material.

GROWTH OF HIGH QUALITY ALINAS BY LOW PRESSURE ORGANOMETALLIC CHEMICAL VAPOR DEPOSITION FOR HIGH SPEED AND OPTOELECTRONIC DEVICE APPLICATIONS

In this paper, we report on the low pressure organometallic chemical vapor deposition of AlInAs lattice matched to InP and the effect of the substrate temperature and V/III ratio on the layers grown. High quality AlInAs with X-ray and photoluminescence (5 K) linewidths of 21 arc sec and 15 meV, respectively, was obtained. It is demonstrated that a high growth temperature and a high arsine flow rate are necessary for obtaining good electrical and optical properties. A discrepancy was shown to exist between C-V and Hall derived carrier concentrations probably due to deep levels affecting the C-V measurements and a two-dimensional electron gas (2DEG) at the AlInAs/InP interface affecting the Hall measurements. The existence of a 2DEG at the AlInAs/InP interface, with a sheet density of 2.9×1011 cm-2 and a mobility of 11050 cm2/V°s at 4 K, was shown using Shubnikov-De Haas measurements. A correlation was made between oxygen or an oxygen related complex and high C-V measured carrier concentrations and large leakage currents in reverse biased Schottky contacts. An intense emission at ~1.2 eV, present in 5 K photoluminescence spectra of AlInAs/InP, was attributed to a spatially indirect transition across the AlInAs/InP interface. Conduction and valence band offsets of 448.8 and 324.3 meV, respectively, were deduced from the energy of this transition. Self aligned 0.25 μm gate high electron mobility AlInAs/GaInAs transistors with a transconductance as high as 1150 mS/mm and ft = 80 GHz at room temperature were fabricated. Finally, metal-semiconductor-metal photodetectors with a leakage current as low as 5 nA at 5 V, breakdown voltage greater than 25 V, responsivity of 0.42 A/W at 1.3 μm wavelength, and a bandwidth of 8 GHz were demonstrated.

Dose‐dependent mixing of AlAs‐GaAs superlattices by Si ion implantation

The effects of Si ion implantation and annealing on AlAs‐GaAs superlattices are examined with secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM). Samples implanted with 180 keV 28Si+ of doses ranging from 3×1013 to 3×1015 cm−2 are examined before and after a 3‐h 850 °C anneal. Both the TEM and RBS channeling data indicate the formation of a heavily damaged surface layer where diffusion of Al is inhibited even after thermal annealing. After annealing, however, significant mixing is observed at depths well beyond the implant range. Depth‐dependent diffusion lengths of Al and Si are derived from the SIMS data. The diffusion coefficient of Si is markedly reduced in the unmixed regions with both the Si and Al concentrations exhibiting abrupt forward and rear diffusion fronts.

The growth and characterization of AlGaAs using dimethyl aluminum hydride

Abstract The growth of AlGaAs by organometallic chemical vapor deposition has traditionally been done using trimethyl aluminum (TMA). The use of TMA, however, leads to a high level of carbon in the AlGaAs layers. In this study, we have investigated the use of dimethyl aluminum hydride (DMAH) as an alternative aluminum source. DMAH is a liquid at room temperature with a favorable vapor pressure of 2 Torr at 25°C. We report on the decomposition studies of DMAH and the growth and characterization of AlGaAs grown using the new compound. Preliminary low temperature PL spectra indicate that carbon acceptors are greatly reduced in layers grown under conditions similar to those used when growing with TMA. These results are supported by our finding the DMAH, when independently decomposed yields high purity aluminum metal, in contrast to TMA which yields aluminum carbides.

Quantum wire lasers by OMCVD growth on nonplanar substrates

Abstract In this paper, we describe the progress made in the fabrication of quantum wire lasers using growth on nonplanar substrates as a lateral patterning technique. GaAs/AlGaAs quantum wire injection lasers with up to three crescent-spaped quantum wire active regions have been fabricated. The lowest threshold current of 2.4 mA was obtained for lasers with 2 quantum wires. We also report on two techniques for the fabrication of quantum wire arrays in GaAs/AlGaAs. Finally, we present our results on an attempt to fabricate quantum wire lasers based on InP, and propose possible solutions to the problems encountered.

InGaAs/InP superlattice mixing induced by Zn or Si diffusion

Recent studies have shown that Zn diffusion preferentially induces mixing (interdiffusion) of In and Ga in unstrained InGaAs/InP superlattices, with little diffusion of the anions. In the present study, a 3.1% lattice mismatch is accommodated in the mixed superlattice with no observable defects in layers on the order of the predicted critical layer thickness. At high concentrations, Zn resides preferentially in the InP layers in the form of Zn3P2. In marked contrast to this behavior of Zn, Si diffusion is observed to cause comparable interdiffusion on the cation and anion sublattices within a narrow range of dopant concentration. This result is at odds with some recent mixing models and is consistent with a divacancy mixing mechanism.

Interface Control in GaAs/GalnP Superlattices Grown by OMCVD

Abstract In this paper, we show that the deleterious effect of the reaction of arsine with the underlying GaInP, when growing GaAs on GaInP, can be overcome by the growth of a thin (≈0.8 nm) GaP interfacial layer. In addition, we show the usefulness of X-ray rocking curve simulations in aiding the understanding and thereby control of heterointerfaces. Variable low temperature photoluminescence measurements were used to confirm the existence of a low bandgap interfacial layer at the GaInP to GaAs interface, predicted from X-ray simulations, by comparing the energy separation between heavy- and light-hole emissions in samples with and without such interfacial layers. The X-ray simulations and photoluminescence measurements also indicated an In contamination of the GaAs quantum well. The source of the In contamination was shown to be the susceptor, which is coated with In based compounds. Both In and As contamination can be a problem in reactors where the carrier gas flows over the susceptor before arriving at the substrate.

Selective organometallic vapor phase epitaxy of Ga and In compounds: a comparison of TMIn and TEGa versus TMIn and TMGa

Abstract The present experiments show that using TEGa as the Ga source in selective OMVPE leads to a higher growth rate enhancement of GaAs and GaP than using TMGa. The combination of TEGa with TMIn ( + AsH 3 or PH 3 ) yields a lower In enrichment of selectively grown GaInAs and GaInP than TMIn + TMGa. These results agree with our previous hypothesis that the differences in growth rate enhancements observed in selective OMVPE can be related to the differences in the extents of decomposition of the source species above the mask, since the decomposition temperature of TEGa is much lower than that of TMGa. We also explain why, although the decomposition temperatures of TEGa and TMIn are similar, there is still a discrepancy in the growth rate enhancements of the Ga and of the In binaries selectively grown using these source reagents.