Realization of high detectivity mid-infrared photodiodes based on highly mismatched AlInSb on GaAs substrates

Abstract

We have systematically investigated highly mismatched AlInSb photodiodes grown on GaAs substrates operating in the mid-infrared range. A novel characterization method was introduced to analyze the recombination mechanism within an active layer of the devices, which revealed a high conductance stemming from the leaky behavior of dislocations. The introduction of a dislocation filter layer successfully reduced threading dislocations and improved resistance area product of photodiodes, leading to high detectivity at room temperature.

InAsSb photodiodes grown on GaAs substrates for long-wavelength-infrared gas-sensing applications

“…Dislocations have previously been shown to detrimentally affect electrical properties in narrow-bandgap materials such as AlInSb ternary alloys [16,17]. The occurrence of the abovedescribed bend in the EQE curve at low injection current density (figure 5(b)) indicated that dislocations also affected device performances of the InAsSb PDs.…”

“…As the thickness of the active layer was increased, higher absorptances were observed, leading to higher responsivity levels due to the increased optical density. However, a thicker active layer would also lead to lower resistance because of increased rate of carrier recombination within the active layer, which would cause a reduction in the detectivity [17]. Therefore, in order to achieve the best tradeoff here, the active layer thickness was set to 2.4 µm in this study, where reflectance and absorptance show local minimum and maximum respectively.…”

“…First, a 0.5 µm thick Sn-doped n + -InSb buffer layer was grown at 410 • C on a thermally cleaned GaAs substrate, followed by a 1.1 µm thick Sn-doped n + -Al 0.09 In 0.91 Sb buffer layer. Two dislocation filter layers, which are 20 nm thick Sn-doped (n + ) Al 0.32 In 0.68 Sb layers, were inserted within the buffer layer to reduce the density of dislocations by confining them within strained layer interfaces [16,17]. Then, a 2.4 µm thick Zn-doped InAs 0.13 Sb 0.87 active layer was grown, which was sandwiched between 20 nm thick Sn-doped (n + ) Al 0.18 In 0.82 Sb and Zndoped (p + ) Al 0.18 In 0.82 Sb as hole-and electron-blocking barrier layers, respectively.…”

Fabrication of highly lattice mismatched AlInSb diodes on GaAs substrates for thermophotovoltaic cells

“…We used two separately embedded 20 nm-thick n-Al 0.31 In 0.69 Sb layers in n-Al 0.09 In 0.91 Sb intermediate layers as a dislocation filter structure. These dislocation filter layers were strained due to the difference in lattice constant, which made it possible to confine and annihilate those dislocations in the interfaces [16][17][18][19][20][21]. Then, a 2.35 µm-thick intrinsic Al 0.09 In 0.91 Sb active layer, which corresponds to the bandgap of 0.31 eV, was grown that was sandwiched between a 10 nm-thick Sn-doped (n + ) Al 0.31 In 0.69 Sb layer and a Zn-doped (p + ) Al 0.31 In 0.69 Sb layer as hole-and electron-blocking barrier layers, respectively.…”

“…Due to the highly mismatched nature of AlInSb/GaAs interface, a large number of dislocations are introduced into the film structure (∼10 9 cm −2 ). However, dislocation filtering [16][17][18] and strain-controlled film structures have been proposed to overcome this problem, leading to high-performance mid-infrared optoelectronic devices, such as light-emitting diodes and photodiodes [19][20][21]. Therefore, AlInSb alloy could become a promising candidate for highperformance thermophotovoltaic cells.…”