Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures Processing Measurement and Phenomena · 2008 · 11 citations · 27 references
Natural SciencesMaterials EngineeringMaterials ScienceElectronic MaterialsMaterials ChemistrySemiconductor MaterialsDefectsDefects In Electronic MaterialsEpitaxial GrowthSemiconductor DefectsX-ray CrystallographyX-ray DiffractionDefect DensityDefect FormationEnergy Dispersive X-ray SpectroscopyEnergy-dispersive X-ray SpectroscopyHigh-resolution X-ray DiffractionMolecular Beam EpitaxyPrecipitatesTemperature-dependent Growth
A systematic study of the evolution of the defect morphology and crystalline quality in molecular beam epitaxially grown CdxHg1−xTe epilayers with growth temperature is presented. The layers were characterized with optical microscopy, atomic force microscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, and high-resolution x-ray diffraction. Four types of defects (microvoids, hillocks, high-temperature voids, and needles) were characterized on epilayers grown in the growth temperature range 188.9−209.9 °C. There is a minimum in the area covered by defects at a temperature just below the onset of Te precipitation, which is defined as the optimal growth temperature. Microvoids with various shapes, and at various stages of growth, were observed side-by-side in many of the CdxHg1−xTe layers, along with hillocks and needles. The defect density of microvoids changes by several orders of magnitude in the studied temperature range. A mechanism for the formation of microvoids and needles is suggested. High-temperature voids associated with Te precipitates appear above the optimal growth temperature. The onset of Te precipitation is well described by a thermodynamic model.
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