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Highly strained InxGa1-x As/InP quantum wells grown
by solid source MBE for applications in the 2-2.3 µm
spectral range
S. Jourba, Michel Gendry, P. Regreny, G. Hollinger
To cite this version:
Highly strained InVGa\VAs/InP quantum wells grown by solid
source MBE for applications in the 2}2.3
lm spectral range
S. Jourba*, M. Gendry, P. Regreny, G. Hollinger
Laboratoire d'Electronique-LEAME, UMR CNRS 5512, Ecole Centrale de Lyon, 69131 Ecully cedex, France
Abstract
High-quality pseudomorphic InP/InVGa\VAs/InP (x"0.85, 0.90) quantum wells have been grown by solid source molecular beam epitaxy using As and P valved cracking cells under standard growth conditions. Photoluminescence measurements at 77 and 300 K were used to characterize the optoelectronic quality of the "lms and the maximum operating wavelength. Promoting a 3D growth mode allows to extend the operating wavelength at 300 K up to &2.3lm. 1999 Elsevier Science B.V. All rights reserved.
Keywords: InGaAs/InP; Strained quantum wells; SSMBE; Photoluminescence
1. Introduction
Compressivelly strained InVGa\VAs quantum wells (QWs) grown on InP are key structures for semiconductor optoelectronic devices operating in the 1.7}2.1lm spectral range [1,2]. For example, the room-temperature operation of In Ga As quantum well laser emitting at 2.07lm has been demonstrated recently [2]. As another example, thin narrow-band-gap absorbing layers embedded in a wide-band-gap material (single quantum well con"guration) and located into a resonant cavity, are particularly attractive to develop high-detectiv-ity infrared photodetectors [3].
The extension of wavelength over 2.1lm is of great interest due to numerous potential applica-tions in gas detection and remote sensing. Higher
* Corresponding author. Tel.: 4-72-18-60-86; fax: #33-04-78-43-35-93; e-mail: jourba@ec-lyon.fr.
wavelength can be achieved with InVGa\VAs QWs either by increasing the In content or the quantum well thickness. However, the onset of plastic relax-ation at a critical thickness of pseudomorphic growth is a limitation to maintain good optoelec-tronic quality [4]. Depending on the indium con-tent x, relaxation of strain can occur either through plastic relaxation (x(0.82) or through the island-ing of the growth front [5]. As relaxation can be controlled by kinetic (growth temperature) and en-ergetic (surface reconstruction) factors [6], MBE performed at moderate temperature appears parti-cularly adapted to reach the highest wavelength. A number of methods have been proposed to in-crease the MBE critical thickness. For example, TournieH et al. [7] have shown that decreasing the growth temperature and using virtual surfactant conditions (In stabilization) allow the growth of high-quality InAs QWs. However, such an ap-proach needs growth interruptions and low growth
Table 1
Description of the sample parameters, growth conditions and photoluminescence spectra parameters of the studied QWs
In mole L/5 (As) ¹(3C) RHEED pattern j (RT) j (77 K) FWHM (77 K) Device
fraction, x (nm) (nm) (meV) quality
Bu!er QW 85 50 490 (2;4) (2;4) 1905 1729 13 Yes 85 75 490 (2;4) (2;4) 2161 1971 10 Yes 85 95 490 (2;4) (2;4) 2195 1991 22 No 90 50 490 (2;4) (2;4) 1993 1857 34 Yes 90 75 480 (2;4) (2;4) 2230 2067 35 Yes 90 75 460 (2;1) 3D 2284 2112 45 Yes
temperatures which make this method hardly ap-plicable to device fabrication.
Before trying such nonconventional growth tech-niques, we chose in this work to de"ne the limits of the InGaAsP system when InGaAs/InP QWs are grown under easily reproducible standard growth conditions. Some works have already been pub-lished for InAs/InP QWs showing room-temper-ature PL emission up to 2.2lm [8]. However, the device quality of these structures was questionable due to partial plastic relaxation, as reported by the authors. Using solid source MBE, we have deter-mined the optimal In composition and growth tem-perature for device quality InGaAs/InP single QWs.
2. Experimental procedure
All samples were grown by SSMBE using As and P valved cracking sells (from RIBER) on InP : Fe (1 0 0) epi-ready substrates supplied by InPact. Be-fore growth, InP substrates were deoxidized under P #ux at 5253C for 30 s. For most samples, the growth temperature was 4903C. The growth rates were &0.9lm/h for InP and &1.1 lm/h for the InGaAs quantum well. The V/III ratios were 40 for InP and 20 for InGaAs. All structures consist of a 0.4lm InP bu!er layer, a compressivelly strained InGaAs QW and a 0.3lm InP cap layer. To take into account the As and P #ux transients, a 10 s growth interruption was performed to switch from InP to InGaAs and vice versa. All structures were undoped.
Room-temperature (RT) and 77 K
photo-luminescence (PL) measurements were performed on all samples. An AlGaAs laser diode emitting at j&800 nm and liquid nitrogen cooled InAs de-tector have been used for excitation and detection, respectively. The spectral resolution of the mono-chromator is about 5 nm. Room-temperature absorp-tion measurements were performed on back-side polished samples.
3. Results and discussion
Two sets of samples were grown:
InP/In Ga As/InP QWs with 50, 75 and 95 As thickness; InP/In Ga As/InP QWs with 50 and 75 As thickness. Sample parameters, growth conditions and PL spectra parameters are shown in Table 1. Fig. 1 presents RT, 77 K PL and RT absorption spectra for In Ga As QWs, while Fig. 2 shows RT and 77 K PL spectra for In Ga As QWs. Note that pseudomorphic QWs with lower or higher In contents (not present-ed here) lead always to lower wavelengths or to poor optoelectronic quality.
For the three In Ga As structures, the growth mode is always 2D as observed by RHEED (strong 2;4 surface reconstruction pattern). All the samples are mirror like. Only for the 95 As sample, Normarski microscopy reveals a few isolated short dislocations in the [1 !1 0] direction, indicating that the QW width is nearly equal to the critical thickness for plastic relaxation. PL linewidths at 77 K for the 50 and 75 As wells are equal to 13 and
Fig. 1. Photoluminescence spectra taken at 77 and 300 K and absorption spectra (300 K) for InP/In Ga As/InP QWs with di!erent well thickness: (a) ¸"50 As; (b) ¸"75 As; and (c) ¸"95 As.
10 meV, respectively, indicating high-quality inter-faces. This is con"rmed by clearly resolved ex-citonic features observed in RT absorption spectra. There is about 1% absorption per well due to the
c1-hh1 transition (1.4}1.5% at exitonic resonance).
PL intensities for 50 and 75 As QWs are comparable to that for lattice-matched In Ga As/InP QWs, while a decrease (by a factor of 6 at RT) is observed for the 95 As well. This is associated with the onset of plastic relaxation. Electrical character-ization of corresponding p}i}n diodes has con-"rmed that only 50 and 75 As QWs have device
quality [9]. Thus, the maximum operating
wavelength for this composition is &2.2lm. For 50 and 75 As In Ga As QWs grown at 4803C, the growth mode is 2D as shown by strong 2;4 RHEED patterns. A maximum wavelength of 2.23lm is achieved for 75 As QW. Both structures have device quality properties. However, PL
Fig. 2. Photoluminescence spectra taken at 77 and 300 K for the InP/In Ga As/InP QWs: (a) ¸"50 As; (b) ¸"75 As grown in`2Da mode; and (c) ¸"75 As grown in `3Da mode.
spectra show a signi"cant broadening of the c1-hh1 transition to about 35 meV at 77 K (Table 1). As 3D islanding e!ects have to be rejected, broadening could arise only from composition inhomogenei-ties. On reaching x"0.9, we believe that lateral composition modulation can be an e!ective mecha-nism of accomodation of the strain energy, as was shown in several systems [10]. In our system, com-position modulation could be associated to In}Ga and/or As}P strain-driven exchange.
surface, due to some surface roughness/disorder. Consequently the 2D/3D growth mode onset oc-curs earlier than for a (2;4) surface. Fig. 2 shows that the 3D In Ga As QW is redshifted with respect to the 2D QW, without a signi"cant de-crease of the PL e$ciency.
4. Conclusion
In this work, we have studied the optical proper-ties of highly strained InVGa\VAs/InP single quantum wells grown by SSMBE under standard conditions. The optimal indium composition for maximizing the operating wavelength was found in the 0.85}0.9 range. A maximum wavelength of 2.23lm is achieved for In Ga As, grown at 4903C. Promoting the 2D/3D growth mode transition at 4603C allows to reach 2.28lm.
References
[1] S. Forouchar, A. Ksendzov, A. Larson, H. Temkin, Elec-tron. Lett. 28 (1992) 1431.
[2] M. Mitsuhara, M. Ogasawara, M. Oishi, H. Sugiura, Appl. Phys. Lett. 72 (1998) 3106.
[3] B.N. Sverdlov, A.E. Botchkarev, N. Teraguchi, A.A. Salva-dor, H. Markoc, Electron. Lett. 29 (1993) 1019.
[4] H. Temkin, D.G. Gershoni, S.N. Chu, J.M. Vanderberg, R.A. Hamm, M.B. Panish, Appl. Phys. Lett. 55 (1989) 1668.
[5] M. Gendry, G. Hollinger, Semiconductor Heteroepitaxy: Growth, Characterisation and Device Application, World Scienti"c, Singapore, 1995, p. 572.
[6] M. Gendry, G. Grenet, Y. Robach, P. Krapf, G. Hollinger, Phys. Rev. B 56 (1997) 9271.
[7] E. Tournie, O. Brandt, C. Giannini, K.H. Poog, J. Crystal Growth 127 (1993) 765.
[8] M. Hopkinson, J.P.R. David, P.A. Claxton, Appl. Phys. Lett. 60 (1992) 841.
[9] S. Jourba et al., unpublished.
[10] T. Okada, G.C. Weatherly, D.W. McComb, J. Appl. Phys. 81 (1997) 2185.
