ISSN:1071-1023    

DOI:10.1116/1.582767

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

We report structural and optical data on single and multiple GaAs–AlxGa1−xAs quantum well structures. The layers were grown in a fully automated system incorporating a high speed rotation stage of our own design. All layers were grown in the substrate temperature range 680–700 °C using an As2source. Growth rates were normally about 1 μm/h for GaAs. The substrate rotation stage is capable of operation at up to 200 rpm compared to commercial equipment operating limits of about 10 rpm. This enables rotation of the substrate once during the deposition of each monolayer, thus avoiding the modulation of alloy composition found at lower rotation speeds. We present data showing the excellent layer uniformity obtained with this device. We have carried out TEM and photoluminescence studies on single quantum well structures grown with and without a prelayer of AlAs. The well with the prelayer shows a peak assigned to then=1(e−hh) free exciton and a considerable decrease in impurity related luminescence at 6 K. We relate these results to improvements in structural properties seen in TEM. Multiple quantum well structures have been grown showing strong photoluminescence up to 300 K. Peaks assigned to then=1(e−hh) andn=1(e−lh) transitions have been observed at room temperature and the possible excitonic nature of these peaks is discussed.

ISSN:1071-1023    

DOI:10.1116/1.582768

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

Persistent photoconductivity (PPC) is studied in modulation doped AlGaAs–GaAs heterostructures in the conductivity parallel to the heterojunctions. The results indicate that the macroscopic fields of the heterojunction and traps primarily in the GaAs rather than AlGaAs are responsible for the phenomenon. PPC is also reported inn+GaAs–undoped AlGaAs–n+GaAs heterostructures for current perpendicular to the heterojunctions.

ISSN:1071-1023    

DOI:10.1116/1.582769

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

The luminescent properties of thin single quantum well AlxGa1−xAs/GaAs structures grown by molecular beam epitaxy were investigated. Since the photoluminescence response of these structures is dominated by the quality of the heterointerfaces, and particularly the inverted heterointerface, the effect of using several different types of interfaces was investigated. In structures with conventional abrupt heterointerfaces, only weak luminescence dominated by extrinsic processes was observed. By grading the Al mole fraction over ∼150 Å region at the heterointerface, an eightfold improvement in the excitonic photoluminescent intensity was obtained. By inserting a three‐period superlattice of graded average composition, a 160‐fold improvement in the excitonic photoluminescent intensity over the abrupt interface structure was obtained. The effect of using dimeric arsenic was also investigated. Since these structures provide feedback as to the quality of the heterointerfaces they can be used as a means of finding ways to improve them.

ISSN:1071-1023    

DOI:10.1116/1.582770

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.582771

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

InAsSb strained‐layer superlattices (SLS’s) are proposed as novel III–V semiconductor materials with the potential for long wavelength intrinsic detector applications. Theoretical studies of the band gaps of various InAs0.4Sb0.6/InAs1−xSbxSLS’s withx>0.6 have been carried out. The results indicate that the wavelength response of various SLS’s withx≳ 0.73 can be extended to 12 μm at 77 K through the intentional use of layer strains. These new structures offer the metallurgical and processing advantages of III–V semiconductors for 12 μm detector applications. Further advantages include a weaker dependence of the SLS band gap on composition and reduced band‐to‐band tunneling in the SLS compared to bulk Hg0.8Cd0.2Te.

ISSN:1071-1023    

DOI:10.1116/1.582772

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.582773

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

The effects of strain and layer thickness on the growth of InxGa1−xAs–GaAs strained‐layer superlattices (SLS’s) by molecular beam epitaxy (MBE) is investigated. Data are presented on two series of InxGa1−xAs–GaAs SLS’s withx∼0.38 andx∼0.28. All of the SLS’s were grown consecutively with all fluxes and growth conditions remaining constant throughout. The only variation in the sample growth within each series was the layer thickness (shutter timing), which ranged from ∼20 to ∼800 Å. The growth rate for all the SLS’s is found to be constant and in close agreement with that predicted from much thicker layers. X‐ray diffraction analysis of the SLS’s shows substantial broadening of diffracted peaks on highly mismatched SLS’s with relatively thick layers, although diffraction patterns of thin‐layer SLS’s and thick single layers of InxGa1−xAs remain sharp. Scanning electron microscopy indicates the broadening in x‐ray diffraction peaks is accompanied by an increased presence of structural defects in thick‐layer SLS’s.

ISSN:1071-1023    

DOI:10.1116/1.582774

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.582775

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

Thermally stable GaAs substrates are needed for ion implantation and active layer growth for the fabrication of microwave devices and integrated circuits. The outdiffusion and redistribution of impurities and related deep levels from GaAs substrates during molecular beam epitaxial (MBE) growth is shown to affect interface quality and device performance. The present paper supports substrate annealing and repolishing as an impurity gettering technique prior to epitaxial growth to reduce interface and surface accumulation of unintentional substrate related impurities. The accumulation of impurities at the surface of GaAs substrates after prolonged annealing is identified by photoluminescence. Epitaxial layers grown on annealed substrates have reduced interface and surface accumulation of substrate related impurities as identified by secondary ion mass spectroscopy and capacitance–voltage profiling. The reduction of these substrate related impurities is observed to be important in the growth of homojunctions and heterojunctions by MBE.

ISSN:1071-1023    

DOI:10.1116/1.582776

出版商:American Vacuum Society    

年代:1984

数据来源: AIP