An electron microscopy study of the effects of annealing on the defect structure of heavily silicon-doped gallium arsenide

Abstract

The lattice defects in heavily silicon-doped gallium arsenide crystals grown by the horizontal Bridgman method were examined as a function of heat treatment and silicon concentration by using transmission electron microscopy. The substructure of as-grown crystals, containing =4 x l O l 9 Si/cmS exhibited the presence of numerous extrinsic stacking faults lying on t h e { 111) and small vacancy type prismatic dislocation loops lying parallel t o the { 110) planes of GaAs. Annealing these crystals at 1100 "C for 15 minutes and quenching to room temperature caused the disappearance of both types of defects and produced a homogeneous solid solution. However, a second heat treatment of the homogenized samples a t temperatures in the range GOO to 850 "C produced additional prismatic dislocation loops, the size, concentration and distribution of'which exhibited an anomalous temperature dependence. More lightly Si-doped [(Si) N 1 x 101scm3] and undoped GaAs crystals grown by the Bridpman method did not exhibit the presence of prismatic dislocation loops or extrinsic stacking faults when subjected to heat treatments similar t o those mentioned above. However, annealing of the lightly doped crystals a t 750 "C for 100 hours resulted in the formation of helical dislocations. The origin of the lattice defects observed in Si-doped GaAs and their behavior during various annealing treatments are discussed and the role of silicon in defect production and annealing is delineated.Die Gitterstorungen in stark mit Si dotierten Galliumarsenid-Kristallen, die nach der horizontalen Eridgman-Methode gezogen wurden, werden in Abhangigkeit von der Temperung und Siliziumkonzentration mit Transmissions-Elektronenmikroskopie untersucht. Die Substruktur der unbehandelten Kristalle, mit ~4 x 1018 Si/cm3 zeigt die Anwesenheit von zahlreichen durch Fremdstorungen verursachten Stapelfehlern auf den { 11 1) -Ebenen und kleinen prismatischen Versetzungsschleifen vom Leerstellentyp, parallel zu den { 110) -Ebenen von GaAs. Das Tempern dieser Kristalle fur 15 Minuten bei 1100 "C und Abschrekken auf Zimmertemperatur verursacht das Verschwinden von beiden Defekttypen und ruft eine homogene feste Losung hervor. Jedoch verursacht eine zweite Temperung der homogenisierten Proben bei Temperaturen im Bereich von 600 bis 850 "C zusltzliche prismatische Versetzungsschleifen, deren GroBe, Konzentration und Verteilung eine anomale TemperaturabhLngigkeit zeigt. Schwacher Si-dotierte (Si = 1 x 101*/cm3) und undotierte GaAs-Kristalle nach der Bridgmanmethode zeigen nicht die prismatischen Versetzungsschleifen oder durch Fremdstorstellen verursachten Stapelfehler, wenn sie ahnlichen Temperungsverfahren unterworfen werden. Jedoch verursacht eine Temperung leicht dotierter Kristalle von 100 Stunden bei 750 "C die Bildung von Schrauben-Versetzungen. Die Ursache der Gitterdefekte, die in Si-dotiertem GaAs beobachtet werden, und ihr Verhalten wahrend verschiedener Temperungsverfahren werden diskutiert und die Rolle des Siliziums bei der Hervorrufung der Defekte nnd der ...

TEM and HAADF STEM Imaging of Dislocation Loops in Irradiated GaAs

“…and co-workers concluded that the loop-like defects on {110} planes present in 300 keV proton bombarded (10 15 to 10 16 H + cm −2 ) n-type Si-doped GaAs annealed in the range 500 • C to 900 • C were hydrogen filled vacancy loops (called hydrogen platelets) [3][4][5] which, due to the gas pressure inside the loops, would appear to be of interstitial nature [3]. This conclusion was supported by still earlier reports of vacancy loops on {110} planes observed in Si-and Te-doped GaAs annealed at high temperatures [6][7][8] and the fact that for low dose electron irradiated n-type GaAs, pointdefect annealing already occurs in the temperature range 200 to 300 • C, which is evidence for point defect mobility in this temperature range [9]. The new data presented in this paper allows for a reinterpretation of the older defect models in proton bombarded n-type GaAs, i.e.…”

Dislocation multiplication in GaAs : inhibition by doping

“…The above mentioned phenomena seem to correspond to the behaviour of GaAs doped with Si [28], Se [26,27] and S [29] as well. On the contrary, Zn doping gives neither loops nor stacking faults, even at concentrations above 1019 at.cm-3 [26,27,29].…”

“…In the case of Si doped GaAs [28], annealing at 1100 °C yields to a homogeneous solid solution. A further annealing at 750 °C with [Si] = 4 x 1019 at.cm-3 causes the formation of a large quantity of small loops, when at 600 and 800 °C, a small number of large loops develops.…”

“…A further annealing at 750 °C with [Si] = 4 x 1019 at.cm-3 causes the formation of a large quantity of small loops, when at 600 and 800 °C, a small number of large loops develops. This anomalous behaviour has been explained by taking into account the formation of (SIGa-VGa) complexes [28].…”

Parallelogram-Shaped and Triangular Defects in GaAs

“…Darby et al [14] attributed the triangular faulted defects in Zn-diffused Si-doped GaAs to Zn precipitation. In addition, stacking faults on the {111} planes in heavily Si-doped Bridgman-grown GaAs have been attributed to Si precipitation [20][21][22]. Although these defects have also not been reported in Si implanted GaAs [15][16][17], they have been observed in very highly Si-doped gradient freeze grown GaAs [8,18,19].…”