The incretise of t h e growth tetiiperatrire diiring t h e SSD process causes a rise of t h e growth rate of t h e Gap. Hall effect anti 1)tiotolutriiiiescriice iiieasureiiieiits as well a s clieinical atia.lysis were rivet1 t o investigate t h e ctiaiige of t h e contents of residual iiiipurities in t h e %a€' in del)eiitleiice on t h e growth teiiiperatrire.Carbon was detected to be t h e tloiiiiriatitig shallow acceiitor in t h e uiitIo~)etl I)-tyl)e SSD-GuP. Its colicelitratioti increases clearly with raising growtli tetiil)eratiiro whereas for S airtl N ititlirectly can I)e coricluded t h a t their concentrations cliiiiinish. Carbon and silicoii ttre incorporated in t h e G a p in p a r t iu electrically inactive forill.1 1 1 all saiiil)les exists I)esitle tlie shallow acceptor a nrecliu~n deep acce1)tor t h e conceiitratiori of which is strongly correlated to t h a t of the carLon acceptor. The Iiiwiiiesceiicespectra of t h e 1)-type saiiiples show a ty1)ical broad band with it ~iiaxiiiiuiii at 1.90 eV whose or@ i s discussed.Die Erhiihirtig tler Ziictitirngsteiii~~eratrir h a t eiii Anwachseii tler Gescliwiiidigkeit cler Ual'-l(risttilliutttioti beiiii SSD-Verltthreii zur Polge. Halleffekt-u i i d Lutiiitieszeirziiiessiiriget1 sowie tlie clieiiiisclro Analyse wiirtleii eingesetzt, 11111 die Veriiii(1eriiiig der ReststiirstelleiikonzeiitratioiieIi i i i i G a p init der Zuclitrriigstein1,eratiir zu verfolgeii.Kotilenstoff wrirtle als clotiiiiiiereiitler flacher Akzeptor iiii uirdotierteri l)-leitetideii SSDGal' iiachgewieseii. Seine Konzetitration steigt tleutlich tiiit wuchseritier Ziichtiiiigsteiii-I)erutiii*, wiihreirtl fur S r i i r t l N iritlirekt geschlossen werdeii kanii, dal3 ilire Koiizeiitratioiieti abtiehtiien. Kolileiistoff iintl Silizirriii siiid iiii G a P zuni griifjteii Teil elektrisch iiiaktiv eiiigetmut.In alleri l'roberi existiert neben tleiii flacheii Akzeptor eiri iiiitteltiefer Akzeptor, tlesseti Konzeiitratioii streng i i i i t der des C-Akzeptors korreliert ist. Die Luiiiineszenzs1)ektrerr des 1)-leitetideii G a P zeigen eiiie typisctie breite B a d e init eiiieiii Maxiinuiii bei 1,90 eV, dereii Herkuiift diskutiert wird.
Thc influence of the crucible inoving (lowering, rotation) during the SSD growth of G a P on the growth rate and the crystal quality is investigated. The crucible lowering leads to an improvement especially of the crystal quality characterized by the size of the singlc crystalline regions and by the homogeneity of the impurity incorporation. On the othor hand, the crucible rotation yields no noticeable improvements (in the case of constant frequency) or a strong increase of the growth rate connected with a deterioration of the crystal quality (accelerated rotation).Es w i d der EinfluB der Tiegelbewegung (Absenkung, Rotation) wahrend der SSDZiichtung von G a P auf die Wachsturnsrate und die Kristallqualitat untersucht. Die Tiegelabsenkuiig fiihrt insbesondere zu einer Verbesserung der Kristallqualitat, die (lurch (lie GroBe der einkristallinen Bereiche und durch die Homogenitat des Stiirstelleneinbaus gekennzeichnet ist. Zusatzliche Tiegelrotation mit konstanter Drehzahl liefert keine iiierkliche Verbesserung. In1 Falle beschleuriigter Rotation erfolgt eine starke Vergr6Berung dor Wachstunisrate, die jedoch rnit einer Verschlechterung der Kristallqualitat verbunden ist.
-Kristalle, die nach verschiedenen Methoden gezuchtet wurden (Gasphasentransport, Losungszuchtung), zeigen teilweise betriichtliche Differenzen in ihren physikalischen Eigenschaften. Ziel der Arbeit ist es, Zusammenhiinge zwischen der Herstellung von ZnSiP,, der Qualitiit der eingesetzten Ausgangsstoffe und den physikalischen Eigenschaften der halbleitenden Verbindung aufzuzeigen. Messungen des Hall-Effektes, der Leitfiihigkeit, der Lumineszenz und der Protonenruckstreuung ergaben Informationen uber die Perfektion und die Homogenitiit der Kristalle sowie uber Storstellen und Rekombinationszentren, die fiir die verschiedenen Zuchtungsmethoden charakteristisch sind. Der EinfluS der Dotierung durch verschiedene Elemente auf die Eigenschaften von losungsgezuchteten ZnSiP,-Kristallen wurde untersucht.Undoped ZnSiP, crystals grown by different methods (vapour phase transport, solution growth) show in part considerable differences in their physical properties. The connections between growth, quality of the basic materials and the physical properties of ZnSiP, will be shown. Measurements of Hall effect, resistivity, luminescence and backscattering o f protons yielded informations about the perfection and homogenity of the crystals and about the impurities and recombination centres characteristically for the various growth methods. The influence of doping by different elements on the properties of solution grown ZnSiP, crystals was investigated.
The ternary semiconductors of the type 11-IV -V with chalcopyrite structure 2 have been extensively studied in the past by different techniques in absorption and reflection measurements to obtain detailed information on band structure and to show something about the physical properties of the so-called "pseudodirect energy gaps" in these compounds. (For a more recent review concerning this subject see ( l ) , and especially for ZnSiP2 see ( 2 ) . )Absorption measurements of ZnSiP (3), (4) showed that the absorption coef--1
F o r G a P an increase of luminescence intensity at low temperature dependent on excitation t i m e was observed. Crystals grown by the synthesis solute diffusion method (SSD) were fastly cooled from the growth temperature to room temperature. Fig. 1 shows typical cathodoluminescence spectra taken at 81 K after different t i m e s of electron irradiation. The increase of luminescence intensity can be seen clearly. In photoluminescence the s a m e behaviour was observed. The dependmce of the maximum intensities of t h r e e peaks in the photoluminescence spectrum on the laser-irradiation time is shown in Fig. 2. During the first one hour of irradiation a strong enhancement of luminescence intensity can b e seen. After long-time irradiation o r at high excitation intensities saturation is reached.Even after several weeks from the measurements the beam a r e a s could b e readily found on scanning luminescence pictures of the samples. The luminescence intensity of the areas previously irradiated by electrons o r l a s e r light was clearly higher than that in other areas. It is a bulk effect, because after removing 0 . 5 p m from the surface by chemical etching no changes of this behaviour were observed.The unchanged energetic position of the donor-acceptor pair peak (No. 2 ) indicates that the concentration of radiative recombination centers did not increase. Therefore one can conclude that the concentration of non-radiative recombination centers had decreased.A possible mechanism f o r such effects is mu€tiphonon emission at non-radiative centers coupled with REDR. The concept of REDR has been well 1) Silbermannstr. 1, DDR-9200 Freiberg, GDR.
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