High Current Gain In_(0.49)Ga_(0.51)P/GaAs Heterojunction Bipolar Transistors with Double Spacers Grown by Gas Source Molecular Beam Epitaxy

This paper reports the improved performance of the lattice-matched N-p^(+)-n In_(0.49)Ga_(0.51)P/GaAs heterojunction bipolar transistors(HBTs)with undoped spacers grown by the gas source molecular beam epitaxy.A 600ÅGaAs base doped with beryllium at 3 × 1019cm^(-3) and a 1000Å In_(0.49)Ga_(0.51)P emitter doped with silicon at 3 × 1017cm^(-3) have been grown.On both sides of the base,the 50Åundoped GaAs spacers were grown.Devices with emitter area of 100× 100μm^(2) were fabricated by using selective wet chemical etching technique.The measured results of HBTs reveal cood junction characteristics,and the common-emitter current gain reaches 320 at the collector current density of 280 A/cm^(2).

Some Considerations on Energy Levels of Quantum Cascade Lasers

Conduction band non-parabolicity is taken into account and a numerical method is proposed to calculate the electron subband energy levels and corresponding wave functions in the active region of quantum cascade lasers.For a coupled double-well vertical transition mode active region,the calculated △E21=32 meV,△E32=270 meV correspond,respectively,to the energy of an optical phonon and that of a photon at wavelength λ=4.5μm.For a coupled triple-well vertical transition active region,the calculated △E21=32.4 meV,△E32=250 meV correspond to the energy of an optical phonon and the photon energy at wavelength λ=5.0μm.

Experimental Study of InP-Based InAlAs/InGaAs Quantum Well Infrared Photodetectors Operating at the 3-5μm Wavelength Region

Gas source molecular beam epitaxy grown InP-based InAlAs/InGaAs quantum well infrared photodetectors operating at 3—5 pm atmosphere window have been fabricated;their structural,electrical and optical characteristics have been investigated.The detectors show peak response wavelength Ap at 3.85μm,with spectral width AX/Xp of 4.6%and 7.2%at 1 and 5 V bias voltages,respectively.Very low dark current of the detectors has been observed.At 2 V bias the dark current is below InA at 77K and remains low value of 10 nA at 150 K.The background limited infrared performance temperature Tblip as high as 165 K has been measured.

Investigation of Hole Mobility in GaInP/(In) GaAs/GaAs p-Type Modulation Doped Heterostructures

Ga_(0.51)In_(0.49)P/(In)GaAs/GaAs heterostructure is regarded as an excellent candidate for two dimensional hole gas system as it has a large valence band offset ratio.In this paper,we report the hole mobility in GaInP/GaAs and GaInP/In_(0.20)G_(0.80)As/GaAs p-type modulation doped heterostructures grown by gas source molecular beam epitaxy with different p-channels and doping methods.The influences of Be:GaAs cap layer,δ-doping,and strained InGaAs p-channel on hole mobility are discussed,and qualitatively explained by the ionized impurity scattering mechanism.Finally,it was shown that the improvement of hole mobility could be achieved by the δ-doping method combined with strained InGaAs channel.

Some Considerations on Optical Confinement and Free Carrier Confinement of Quantum Cascade Lasers

Calculating the refractive index dispersions considering the influence of doping concentration on refractive indices,we have illustrated the heavily doped contact layers,n=1×10^(19)cm^(-3)forλ~9μm,and n~1 x 10^(20)cm^(-3)forλ=5μm quantum cascade lasers,to suppress the refractive indices and get sufficient optical confinement.By calculating the transmission of energies through a graded gap superlattice,it is demonstrated that for energies E1 and E2(the two lower states)the electrons can easily get through the graded gap superlattice.While for energy E3 the graded gap superlattice creates a minigap(the transmission of the energies E1 and E2 is 102 times more than that of E3).In this way,the electrical confinement can be achieved.