Growth and characterisation of InP by close vapour transport J. Mimila- Arroyo, J. Diaz, A. Lusson, C. Grattepain, R. Bisaro, and J. C. Bourgoin close. .$pdcp lapour trmsport is a tecl~niqcte thcct allo\vs rapid and ine.xpensice epita.uicr1 grobcth using water rapour as the ~rrl~lsporting gcrs. The nwr~her ojparrrrtteters gocernitrg the gobvth is srnoll (source and substrate ternpcrrrture, water capour pdrtiul pressure) err~tl these parameters call be varied ir~depenelrr~tly. Epitcrsial lnP layers hare been gro\cn ctsir~g rl~is technique. The loj.ers \lare hem choracterised h!. double crystal A'-ra! diflrac.tion, secondary ion ttlass spectrortletry, Hall eflect, and phutolun~ir~escer~ce. The ecolution of the mure irnd concentrrrtior~ ojsl~allo~c~ impurities aud deep defictsns ajunction ojrhe growth partrrrreters has been monitored. MST/33?7 1996 The Institute ojMaterials. Dr .\lirnila-Arroyo and Jfr Dia: are at the Centro de Inrestigacion y de Estudios Acanzirdos del I.P..V.. Mkrico. Dr Lussort is in the Laboratoire de Ph~siqcre des Solides, Centre h:utional de la Recherche ScientiJique, ,$feudon. France. Mr Grattepairt and Dr Bisaro are in the Lahorirtoire Central de Recherche. Thornson, Orsay, Frirr~ce. Dr Bourgoirt is ir~ the Groupe de Ph!.siq~re des Solides, Cnirersitks Paris 6 et Paris 7, Frunce. This paper w.irs presented at the lsr interr~ational rorference on .~luterials/or ~1icroelec.trt~nic.s. held in Burcelono, Spain on 17 19 Ortoher 1994. Introduction Indium phosphide is an extensively studied material because of its potential for optoelectronics. Recently, substantial progress has been made in the production of good quality bulk crj-stals for use as substrates. However, because of the sensitivity of such substrates to ther~nal treatment, particu- larly semi - insulating substrates realised by Fe doping. epitaxial growth remains an important part of InP technology. For example, semi - insulating layers and thick epitaxial layers with improved crystallinity and low defect density, grown on conventional substrates, would be advantageous provided they could be realised at low cost. The aim of the present work is to attempt to realise such epitaxial layers at potentially low cost, and to describe their crystalline, electrical, and optical properties. Thsse layers have been grown by a particular chemical vapclur deposition technique using water vapour as the transporting gas: an inexpensive and rapid technique usually termed close space vapour transport (CSVT, see Ref. 1). The properties of the layers produced have been characterised as a function of the growth temperature by electrical measurements, photoluminescence. and double crystal X-ray diffraction. Their chemical content was determined by secondary ion mass spectrometry. Growth technique The epilayers were grown on single crystal, (100) oriented InPwafers produced by the liquid encapsulated Czochralski method and made semi - insulating b!- the addition of Fe. Table 1 Substrate temperature T,, growth rate V,, and thickness e of grown layers and relative photoluminescence intensities P, and P, corresponding to excitonic and donor-acceptor transitions, respectively Pl . p2 9 T,. v,. e, arbitrary arbitrary Sample C pm h-' pm units units PJP, The source material is an undoped wafer with a residual impurity concentration of the order of 10'5cm-3. The growth was carried out in a CSVT reactor. using water as the chemical transporting agent. diluted (to a few parts per million) in a H2 atmosphere. Owing to the size of the reactor, the grown lajers have a diameter of 10-15 mm. The layers were produced with thicknesses varjing from 1 to 3 pm. The growth rate, from 4 to 20 pm h-', was varied by adjusting the substrate temperature in the range 600-760'C. The characteristics of the growth for each layer are given in Table 1. layer characterisation X-RAY DIFFRACTION The crystallographic properties of these layers were first studied using a high performance double crystal X- ray (DXD) spectrometer in the (+I. -I) configuration with a thick Ge crystal as a monochromator. The full width at half maximum (FWHM) of the (004) InP substrate diffraction peak is of the order of 17.4" (see Fig. 1). close to the theoretical value of 11-6". Figure I also shows the typical diffraction pattern on (004) planes of a 1.0 pm thickness layer. From the depth penetration of X- rays, and the slight asymmetry of the top of the diffraction peak ( F W H M of 19.1 and 13.4" for the low and high values of the angle of incidence, respecti\-ely), it can be concluded that two Bragg peaks esist corresponding to the diffractions of the Cu K,, line on the (00.1) planes of the substrate and the layer, respectively. The lattice mismatch is less than 5 x lo-'. The FWHhl of 19.1 and 134" must be ascribed to the layer and the substrate. respectively. Since these \dues are very close to the theoretical value, the structure of the epitaxial layer is nearly perfect. The departure of the lattice parameter of the layx from that of the bulk InP (12-43 suggests the existence of a high impurity content in the epitaxial layer. This result is in agreement with preliminary Hall effect measurements. carried out at room temperature with ohmic contacts formed by In alloying on layers grown on semi - insulating substrates. These showed that the layers are n type with a carrier concentration of the order of ~O''cm-~ and mobilities of the order of 3.0 c m 2 V-' s-' . The existence of donor impurities (S, see below) is related to the purity of the atmosphere, i.e. to the quality of the H2 purifying system. Finally, the high FWHM observed on the edge of the epitaxial layer may 1.78 Mater~als Science and Technoloav Februarv 1996 \I-' 12