Two-dimensional electron gas in InGaAs∕InAlAs quantum wells

Abstract

We designed and performed low temperature DC transport characterization studies on twodimensional electron gases confined in lattice-matched In0.53Ga0.47As/In0.52Al0.48As quantum wells grown by molecular beam epitaxy on InP substrates. The nearly constant mobility for samples with the setback distance larger than 50nm and the similarity between the quantum and transport life-time suggest that the main scattering mechanism is due to short range scattering, such as alloy scattering, with a scattering rate of 2.2 ps −1 . We also obtain the Fermi level at the In0.53Ga0.47As/In0.52Al0.48As surface to be 0.36eV above the conduction band, when fitting our experimental densities with a Poisson-Schrödinger model.Two dimensional electron gas (2DEG) confined in In 0.53 Ga 0.47 As in lattice matched InGaAs/InAlAs/InP heterostructures and superlattices appear in many technologically important areas ranging from high speed electronics[1], optoelectronics [2,3] and spintronics [4,5]. It is also an attractive 2DEG system for the study of disorder induced quantum phase transitions [6,7,8,9,10,11]. While there have been several earlier works characterizing electronic properties of 2DEGs in In 0.53 Ga 0.47 As/In 0.52 Al 0.48 As heterojunctions [12,13,14,15], In 0.53 Ga 0.47 As/InP heterojunctions and quantum wells (QW) [16,17,18], there were few systematic studies characterizing 2DEGs in In 0.53 Ga 0.47 As/In 0.52 Al 0.48 As QWs. Since many modern structures [1,2,3,5] are now based on In 0.53 Ga 0.47 As/In 0.52 Al 0.48 As QWs, such characterization is of fundamental and technological interest.In this letter we report the characterization of electronic properties of 2DEG in a series of lattice matched InGaAs/InAlAs QWs grown by molecular beam epitaxy (MBE) on InP substrate (here and after in our paper we use abbreviations InGaAs for In 0.53 Ga 0.47 As and InAlAs for In 0.52 Al 0.48 As). Systematic investigations of 12 such wafers with varying design parameters in the doping layers have yielded important information not only about carrier mobility and scattering, but also about how doping determines the carrier densities, from which we were also able to determine the location of the Fermi level at the InGaAs surface.The schematics of the samples is depicted in Fig. 1(a) and the parameters for each sample are summarized in Table I. The 2DEG resides in a 20nm-wide InGaAs QW. Two Si δ-doped layers are placed in the InAlAs barrier to one side (closer to the surface) of the QW. The three design parameters that were varied are the doping densities (N t and N b ) in the top and bottom dopant layers respectively, and the distance d from the bottom dopant layer to the (top) edge of the QW. We fabricated standard Hall bars with Indium ohmic contacts. We tried to measure all the samples at dark. Except a few samples (6 − 9) most of them need to be illuminated to create a 2DEG. For these samples we illuminated for sufficient time with an LED to create a 2DEG with the highest possible mobility. We measured the magnetoresistance R xx and the Hall...

Quantum and transport scattering times in AlGaAs/InGaAs nanoheterostructures with AlAs inserts in the spacer layer

“…The electron effective mass for In 0.2 Ga 0.8 As was 0.041 times of the bare electron mass. The quantum scattering time τ q was determined from a Dingle style analysis [23]. It is well known that the amplitude of SdH oscillations ∆R is described by the relation ∆Rsinh(A T )/4R 0 A T = exp(-πω c τ q ), where A T = 2πk B T/ ћω c is the thermal damping factor, the cyclotron frequency is ω c = eB/m ✳ , and R 0 is the zero-field resistance.…”

Электронный квантовый транспорт в псевдоморфных и метаморфных квантовых ямах на основе In-=SUB=-0.2-=/SUB=-Ga-=SUB=-0.8-=/SUB=-As

“…Напротив, в образце 433 с линейной кон- Квантовое время релаксации импульса рассчитано из пиков осцилляций ШдГ по методу Дингла. Амплитудная зависимость осцилляций описывается соотношением [19] Rsh(A T )/4R 0 A T = exp(−π/ω c τ q ), где A T = 2π 2 kT / ω c , ω c = eB/m * . При построении графика Дингла -зависимости ln[ Rsh(A T )/4R 0 A T ] от обратного магнитного поля -точки должны лечь на прямую линию, наклон которой равен πm * /eτ q .…”

Effect of wire length on quantum coherence in InGaAs wires

“…Other parameters depending on µ 2D and N s are evaluated accounting for nonparabolicity in the InGaAs conduction band 43,44 , with a ratio of Γ-point effective mass m * to free-electron mass of 0.0353 and a low T band gap of E g = 813 meV. In the unpatterned 2DES we have the elastic scattering time τ e2D = 0.81 ps, the mean-free-path e2D = 0.59 µm, the Fermi energy E F = 80.4 meV, λ F = 19.9 nm ( W ), and the diffusion constant 45,46 . Measurements occurred in a 3 He cryostat using fourcontact low-frequency lock-in techniques under constant current I = 20 nA, sufficiently low to avoid heating the 2DES.…”