Shallow level recombination current dominance in transistor betas

A new recombination mechanism, via the high density of shallow donor and acceptors present in the base-emitter junction of integrated circuit transistors, is suggested. In contrast to the recombination via deep centers, this mechanism has an ideal voltage dependence, leading to a beta essentially independent of the base-emitter voltage. It appears to be the dominant component to the base current of integrated circuit transistors. The temperature dependence of the beta of the transistors arises from the ionization energy of the donors and acceptors. The rate-setting capture cross section by neutral acceptor and donors is 1.3(5)×10^-5 cm²     

Mg掺杂Al_(0.5)Ga_(0.5)N薄膜的发光性质研究

利用MOCVD技术在c面蓝宝石衬底上采用AlN缓冲层制备了Mg掺杂Al0.5Ga0.5N薄膜。采用CL测试方法研究了Mg掺杂对Al0.5Ga0.5N薄膜光学特性的影响。测量表明,Mg掺杂导致在Al0.5Ga0.5N薄膜的发光谱中出现了3.9eV的发光带,其发光机理为束缚的施主-受主对(DAP)间的辐射复合跃迁。     

Optically detected impurity D and D transitions in GaAs quantum wells

We have carried out a far-infrared magnet-optical study on shallow donor states confined in GaAs quantum wells (QWs), applying a recently developed optical detection technique. We have observed, in addition to cyclotron resonance, the 1s → 2p₊ transition of neutral donors (D⁰), and singlet and triplet transitions of negative donor ions (D⁻); the latter observation verifies the existence of D⁻ ions in well-only doped QWs under optical pumping. This is the first observation of optically detected impurity resonances in confined systems and demonstrates the power and utility of this technique for such studies.     

Residual donors and acceptors in high-purity GaAs and InP grown by hydride VPE

Residual donors and acceptors in epitaxial films of GaAs and InP grown by the hydride vapor phase epitaxy technique were investigated using the complementary techniques of photothermal ionization spectroscopy and variabletemperature photoluminescence. High-purity samples of GaAs grown in three different laboratories were compared and high-purity InP samples were also measured. The dominant shallow acceptors in the GaAs samples were found to be C and Zn, and deep Cu and Mn acceptors were also observed. The donors Si, S, and Ge were observed in the GaAs with S being dominant. A clear correlation was observed between the gas phase stoichiometry during growth and the relative incorporation of column IV donors (Si and Ge) and column VI donors (S) in GaAs. Substrate quality, source purity, and atmospheric contamination of the growth system were found to influence the photoluminescence spectra of the GaAs samples. In the InP samples three shallow acceptors were observed including Zn, an unknown shallow acceptor level with E_A ≃ 21 meV, and an acceptor which may be either C or Mg. An unusual deep, structured emission band was also seen. The donors in the hydride InP were also found to be present in LPE InP and are believed to be Si and S.     

The effect of growth conditions,point defects and hydrogen on the electronic structure and properties of p-type (Al,N) codoped ZnO: A first principles study

The effects of point defects, hydrogen, and growth conditions on the electronic structure and properties of the (Al,N) codoped p-type ZnO have been investigated using the first principles method. The obtained results showed that the Al_Zn–N_O–V_Zn complex is a shallow acceptor that can play an important role in achieving the p-type conductivity in the (Al,N) codoped ZnO films. Our results showed also that the electrical conductivity type in the (Al,N) codoped ZnO films strongly depends on the donor/acceptor concentrations ratio. The codoped ZnO films prepared under both Zn-rich and O-rich growth conditions with a donors/acceptors ratio of 1:2 have a p-type conductivity, while those prepared with a ratio of 1:1 cannot be p-type unless if they are prepared under O-rich conditions. The achieved p-type quality depends also on the used nitrogen doping source. To prepare p-type ZnO film of high quality using the (Al,N) codoping method, the use of NO or NO₂ is recommended. The presence of donor defects such as oxygen vacancies and hydrogen will significantly affect the electronic properties of the (Al,N) codoped ZnO films, and if the concentration of these defects in the sample is high enough, the material can be easily converted to n-type.     

MOS Capacitance-Voltage Characteristics Ⅲ.Trapping Capacitance from 2-Charge-State Impurities

Low-frequency and high-frequency capacitance-voltage curves of Metal-Oxide-Semiconductor Capacitors are presented to illustrate giant electron and hole trapping capacitances at many simultaneously present two-charge-state and one-trapped-carrier,or one-energy-level impurity species.Models described include a donor electron trap and an acceptor hole trap,both donors,both acceptors,both shallow energy levels,both deep,one shallow and one deep,and the identical donor and acceptor.Device and material parameters are selected to simulate chemically and physically realizable capacitors for fundamental trapping parameter characterizations and for electrical and optical signal processing applications.     

GaP：N液相外延层中杂质对PL谱的影响

借助低温光致发光方法测量了ＧａＰＮ双液相外延材料ＰＬ谱，结果表明：辐射复合效率高的材料ＰＬ谱基本上由孤立Ｎ和ＮＮｉ等束缚激子尖锐峰组成；发光效率较低的ＰＬ谱含有ＤＡ对辐射跃迁的钟形谱上迭加ＮＮｉ峰．分析了谱峰的性质，阐明了提高ＧａＰＮ外延片发光效率的制备工艺途径     

Native defects and dopants in gan studied through photoluminescence and optically detected magnetic resonance

Native defects and dopants in GaN grown by organometallic chemical vapor deposition have been studied with photoluminescence and optically detected magnetic resonance. For undoped samples, the combined results indicate the presence of residual shallow donors and acceptors and deep donors. A model for the capture and recombination among these defects is developed. For Mg-doped samples, the experiments reveal shallow and perturbed acceptors and shallow and deep donors. Hence, shallow and deep states for the native donor or donors appear in all samples. The Mg-acceptor is perturbed from its effective-mass state by nearby point defects.     

Optoelectronic properties of n-type CdZnTe 2-DEGsingle-quantum-well heterostructures

Optoelectronic properties of asymmetrically strained II-VI CdZnTe single-quantum-well structures grown by molecular-beam epitaxy are reported. Indium doping CdZnTe n-type using a two-dimensional electron gas heterostructure achieved a carrier mobility of 5000 cm²·V^-1 s^-1 at 40 K. A shallow donor ionization energy of 14.5 meV was determined from Hall effect measurements. Fabrication of a large-area-mesa heterostructure device allowed us to investigate exciton absorption of the mixed type-I and type-II single quantum well. Control of the electron concentration in the quantum well allows optical absorption modulation using both the quantum-confined Stark effect (QCSE) and phase-space absorption quenching. Separation of electron and hole photocurrents in different layers is demonstrated and results in photogain. A heavy-hole red-shift of 9.9 meV/V due to the reverse QCSE is reported     

New shallow acceptor levels in GaAs

Two previously unreported shallow acceptor levels with ionization energies of 25.2 and 43.2 meV, respectively, have been observed in a number of vapor phase epitaxial and metalorganic chemical vapor deposited GaAs samples grown in several different laboratories. The corresponding donor-to-acceptor and conduction band-to-acceptor transitions are identified in low temperature photoluminescence spectra by means of their temperature and excitation intensity-dependence. These levels are present as residual acceptors in high purity material, but their chemical and/or metallurgical nature has not yet been determined. *Present address: Bell Communications Research, Murray Hill, NJ 07974.     

MOS Capacitance-Voltage Characteristics III. Trapping Capacitance from 2-Charge-State Impurities

Low-frequency and high-frequency capacitance-voltage curves of Metal-Oxide-Semiconductor Capacitors are presented to illustrate giant electron and hole trapping capacitances at many simultaneously present two-charge-state and one-trapped-carrier, or one-energy-level impurity species. Models described include a donor electron trap and an acceptor hole trap, both donors, both acceptors, both shallow energy levels, both deep, one shallow and one deep, and the identical donor and acceptor. Device and material parameters are selected to simulate chemically and physically realizable capacitors for fundamental trapping parameter characterizations and for electrical and optical signal processing applications.     

硅中浅杂质的高激发态(英文)

Photothermal ionization spectroscopy (PTIS) has revealed highly excited states of both shallow donors and acceptors in ultra-pure silicon. At least eight discrete lines associated with the highly exeited states that are higher than 6p, level of phosphorus donors have bsen observed in the photothermal ionization spectra of n-type ultra-pure silicon. For p-type ultra-pure silicon, up to 12 discrete lines and fine structures of the lines associated with the excited states of boron acceptors have also been observed. The assignment of the lines has been made and discussed according to the effective mass theory(EMT) of shallow impurities in silicon.     

High-energy (MeV) ion implantation and its device applications inGaAs and InP

The work performed to date on the implantation of megaelectronvolt (MeV) energy ions of shallow donor (Si, S), shallow acceptor (Be), compensation (B, O, N, Fe, Co, Ti), and rare-earth (Er) species in III-V GaAs and InP compounds is reviewed. The optimum annealing conditions, the resulting carrier concentrations, and the lattice quality of the material are discussed. For the buried implants, the lattice damage and the electrical properties of the material are almost independent of the implant energy. For MeV Be⁺ implants the outdiffusion of Be during annealing is not observed, unlike in the case of shallow keV Be ⁺ implants. The MeV energy Fe⁺ or Co⁺ implants performed at 200°C into n-type InP, and Ti implants into p-type InP gave thermally stable buried high-resistance layers. The performance of microwave devices like vertical p-i-n, varactor, and mixer diodes and an optical device like a heterostructure laser made using MeV energy ion implantation is discussed. The results of MeV implantation in obtaining interdevice isolation of multilayer structures like HBTs are also discussed     

InAs quantum-dot lasers operating near 1.3 μm with highcharacteristic temperature for continuous-wave operation

A high characteristic temperature with T₀ of 126 K under continuous-wave operation is obtained for an InAs/GaAs quantum dot laser. A triple-stacked active region with an energy separation of 95 meV between the ground and first excited radiative transitions is used to achieve a ground state saturation gain at 300 K of 13 cm^-1, and high internal quantum efficiency of 74%     

施主受主共掺实现N型ZnS的第一性原理研究

基于密度泛函理论的第一性原理,利用施主受主共掺方案研究了低阻N型ZnS,通过计算得到2Al,帆的共掺形成能为-0．73eV,离化能为73meV,远小于单掺Al的情况。态密度分析表明,2Alzn-Ns共掺后导带向低能方向移动并出现峰值,价带性质几乎不变,导带底的峰值主要由N-3s和Al-3s态贡献。因此,2Ak-Ns共掺可得到低阻N型ZnS。     

New CO2 laser lines in the 11-μm wavelength region:new hot bands

Nineteen new laser lines in the 11-μm wavelength region have been observed in CW oscillation from a CO₂ laser with a high-Q, high-resolution cavity at a higher than usual current density. The frequency of each line has been measured using heterodyne frequency measurement techniques. Analysis of the frequencies shows that 15 lines are rotation-vibration transitions of the 01¹2-[11¹1,03¹1]_I band (the first sequence hot band) of the CO₂ molecule and four lines belong to the rotation-vibration transitions of the 02²1-[12 ²0, 04²0]_I band of CO₂     

Optical properties and recombination mechanisms in GaN and GaN:Mg grown by metalorganic vapor phase epitaxy

Photoluminescence (PL) and reflection spectra of undoped and Mg-doped GaN single layers grown on sapphire substrates by metalorganic vapor phase epitaxy (MOVPE) were investigated in a wide range of temperatures, excitation intensities, and doping levels. The undoped layers show n-type conductivity (μ=400 cm²/Vs, n=3×10¹⁷ cm⁻³). After annealing at T=600–700°C, the Mg-doped layers showed p-type conductivity determined by the potential-profiling technique. A small value of the full width at half maximum (FWHM=2.8 meV) of the excitonic emission and a high ratio between excitonic and deep level emission (≈5300) are evidences of the high layer quality. Two donor centers with activation energies of 35 and 22 meV were observed in undoped layers. A fine structure of the PL band with two narrow lines in the spectral range of the donor-acceptor pair (DAP) recombination was found in undoped layers. An anomaly was established in the temperature behavior of two groups of PL lines in the acceptor-bound exciton and in donor-acceptor pair regions in Mg doped layers. The lower energy line quenched with increasing temperature appreciably faster than the high energy ones. Our data does not agree with the DAP recombination model. It suggests that new approaches are required to explain the recombination mechanisms in undoped and Mg-doped GaN epitaxial layers.     

Characteristics of laser diodes with a partially intermixedGaAs-AlGaAs quantum well

Laser diodes (LD's) with a partially intermixed quantum-well (QW) active layer are fabricated by Zn out-diffusion from a p-cladding layer to the QW region. The dependencies of the degree of intermixing, measured by the photoluminescence (PL) shift, on Zn concentration of the p-cladding layer (P_clad) and the Al content of the guiding layer (X_g) in a separate-confinement-heterostructure (SCH) are investigated. P_clad changes in the range from 1×10 ¹⁸ cm^-3 to 4×10¹⁸ cm^-3 and X_g changes in the range from 0.21-0.37. When P_clad is 2×10¹⁸ cm^-3 and X_g is 0.37, large bandgap energy shift of 96.1 meV is observed. The lasing wavelengths of the LD's, with the partially intermixed QW, are blue-shifted linearly with increasing P_clad and X_g. For the bandgap energy shift of 66.8 meV by PL, the threshold current density is increased by 33% from that of the nonintermixed LD. Reliability of LD's with the partially intermixed QW is investigated for the first time. In spite of a large degree of intermixing the reliability of the LD with the partially intermixed QW of 66.8 meV energy shift by PL is the same as the nonintermixed one, which is confirmed by the aging test of 2500 hours at 45°C with the output power of 1 W under CW operation     

Oxygen and Erbium related donor centers in Czochralski grown silicon implanted with erbium

The Hall effect measurements were conducted on Czochralski-grown silicon after implantation of erbium and two-step annealing at 700 °C and 900 °C. After the first step the formation of oxygen-related shallow donors was observed at E _c in the range 20–40 meV and erbium-related donor centers at ≈E _c -70 meV and ≈E _c -120 meV. Along with the same oxygen-related shallow thermal donors and donor centers at ≈E _c -70 meV, other donor centers at ≈E _c -150 meV are formed following the 900°C anneal, instead of those at ≈E _c -120 meV. The new donor states are of particular interest because of their possible involvement in the photoluminescence process. The obtained results for erbium-implanted silicon are compared with some fragmentary DLTS data found in the current literature on the donors with ionization energies less than 0.2 eV. Fiz. Tekh. Poluprovodn. 33, 1192–1195 (October 1999)     

Luminescence and electrical properties of MgxZn1-xTe alloys

The luminescence and transport properties of high-quality undoped and phosphorus-doped Zn1-xMgxTe alloys (x ≤ 0.50) have been investigated. At 4.2 and 300 K, the photoluminescence of unintentionally doped crystals is dominated by near-band-edge recombination mechanisms. In phosphorus-doped samples, the luminescence spectra exhibit free-bound transitions involving shallow acceptor centers (phosphorus in tellurium sites). Whenxand/orTincreases, a broad luminescence band also appears at lower energy (1.7-1.9 eV) which decreases the near-band-edge luminescence efficiency. This low-energy band could be due to phosphorus atoms occupying other sites in the lattice (metal sites, for example) and then acting like deep recombination centers. Such a behavior could also explain the electrical properties of phosphorus-doped crystals. The introduction of phosphorus leads to an increase of the free hole concentration p as compared to undoped crystals but all phosphorus atoms do not behave as shallow acceptors; an increasing fraction of these atoms would act like donors in sites other than the tellurium sites as x increases. In undoped materials, p decreases drastically when we add more magnesium and the hole mobility remains approximately constant. We think that this effect is due to compensation by residual donor impurities. On these undoped samples, light-emitting diodes (LED's) have been successfully obtained for the first time. Their quantum efficiency is reasonable if we take into account the low carrier concentration of the material. The emission peak position is 5390 Å for Zn0.9Mg0.1Te instead of 5550 Å for undoped ZnTe.