【摘要】 采用改进的气相外延法在(100)GaAs衬底上外延生长了ZnSe单晶膜。最大生长速率为每小时10μm左右。淀积过程的激活能为10kcal/mol。在77K的温度下测量了外延膜的光致发光,4460A附近可以观察到很强的蓝色发射。外延膜的电阻率～1.1Ω·cm。更多还原

【Abstract】 An epitaxial growth of ZnSe single crystalline layer on a GaAs substrate has been performed in a hydrogen flow system using ZnSe powder as source material.Before deposition, machemically polished (100) GaAs substrate is first cleaned in trichroethylene, then in aceton and finally in methanol followed by a rinse in deionized water.The substrate is then etched in a mixture of H2SO4:H2O2:H2O = 3:1:1 for about 1 min. In order to remove surface damage resulting from cutting and polishing of the wafer.The source material and freshly etched substrate are inserted into the respective zones of the reaction tube. The flow rate of the carrier gas H2 is set to 10-40 ml/min, which is controlled by a mass flow controller (M.F.). The source temperature is about 820-850℃.The single-crystalline ZnSe layer is obtained successfully at the substrate temperature range of 550-750℃.The X-ray diffraction analysis, X-ray Laue pattern and reflective electron diffraction analysis of the as-grown layer demonstrat that the layers are single crystalline and have cubic structure. The as-grown surface microphoto-graph and cleavage edge view are presented.The growth rate is found to be proportional to exp(-EA/kT) in the temperature range of 550-700℃, where k is Boltzmann constant, Ea the activation energy and T the growth temperature.The activation energy is 10.5 kcal/mol, which suggests the growth kinetics should be between the mass transfer control case and surface reaction control case.The photoluminescence of epitaxial film is excited by a nitrogen laser (A = 3371 A) with the peak pulsed power of 900kW and measured at 77K and at the room temperature. The PL spectrum at 77K consists of a narrow near- band-edge emission at about 4460 A and a broad emission at longer wavelengths which is attributed to Cu-G emission. The presence of this intrinsic near-band-gap emission line in the PL spectrum even at room temperature sbows the bigh quality of the epitaxial layer.The measurement cf the resistivity and Hall effect are made for epilayers of ZnSe frown on a se-mi-insulating GaAs substrate at room temperature. Ohmic contacts to the ZnSe layers are made by In followed by an annealing step in N2 atmosphere at 350℃ for 3 mins. The resistivity of the as-grown ZnSe is typically 1.1Ωcm. This is attributed to autodoping of Ga impurity from GaAs substrate. The mobility is 114 cm2V-1s-1, and the electron concentration n = 5×1016cm-3. It is shown that ZnSe epilayer grown on (100) GaAs by VPE can be a suitable material for blue-emitting electroluminescent devices.更多还原