Development of 6.00Å graded metamorphic buffer layers and high performance In0.86Al0.14As∕In0.86Ga0.14As heterojunction bipolar transistor devices

Abstract

Structural and morphological properties of GaN buffer layers grown by ammonia molecular beam epitaxy on SiC substrates for AlGaN/GaN high electron mobility transistorsComparison of As-and P-based metamorphic buffers for high performance InP heterojunction bipolar transistor and high electron mobility transistor applications In x Al 1−x As/ In x Ga 1−x As heterojunction bipolar transistors ͑HBTs͒ with lattice parameters ranging from 6.00 to 6.058 Å employing the use of narrow band gap In x Ga 1−x As base epitaxial layers toward InAs ͑0.86Ͻ X ln Ͻ 1͒ allows for the development of high speed digital and mixed signal circuits to perform at half the power required for conventional group III-V-based HBT device technologies. However, one of the key challenges inhibiting the development of low power narrow band gap HBT device circuits is the absence of semi-insulating ͑SI͒ substrates with lattice parameters towards 6.058 Å. Therefore, a metamorphic In x Al 1−x As ͑0.52Ͻ X ln Ͻ 0.86͒ graded buffer layer ͑GBL͒ grown on InP by molecular beam epitaxy was investigated as a means to enable a SI template with a lattice parameter of 6.00 Å. The metamorphic In x Al 1−x As GBL thickness is desired to be less than a micron in order for this approach to be compatible with the aggressive design rules of high-density transistor circuits. In this study, In 0.86 Al 0.14 As/ In 0.86 Ga 0.14 As double heterojunction bipolar transistor devices were grown on 0.90, 0.45, and 0.23 m thick In x Al 1−x As GBLs to assess the role of buffer layer thickness on both defect formation and device performance. The material characterization results for the 0.90 and 0.45 m thick buffer layers exhibited a crosshatch pattern with a surface rms roughness of 4 nm and threading dislocation densities of ϳ10 6 cm −2 . Excellent dc and rf characteristics from metamorphic HBT devices with submicron emitter widths were observed with low turn-on voltage of 0.45 V, high current gain, low reverse junction leakage ͑Ͻ1 A͒, and rf peak performance in the vicinity of 150 GHz. Finally, preliminary circuits ͑dividers and delay chains͒ have been designed, fabricated, and demonstrated with the 6.00 Å HBT technology.

Low-Temperature and Metamorphic Buffer Layers

“…Buffer layers with linearly-graded composition, and therefore lattice constant, have been extensively investigated in a number of material systems, including In x Ga 1Àx As/GaAs [25,26,51,[96][97][98][99][100][101][102][103][104], In x Al 1Àx As/GaAs [34,75,103,[105][106][107][108][109][110], In x Al y Ga 1ÀxÀy As/GaAs [18,19,23,35,80,95,111], Si 1Àx Ge x /Si [112][113][114][115][116], In x Ga 1Àx P/GaAs [117][118][119], In x Ga 1Àx P/ GaP [120], ZnS y Se 1Ày /GaAs [102,121], and In x Ga 1Àx Sb/GaSb [122,123]. A possible advantage of continuous grading is that layer-by-layer growth may be maintained without the intrusion of island growth associated with large, abrupt changes in composition [119].…”

“…Metamorphic HBTs [117,118,140] and double heterojunction bipolar transistors (DHBTs) [107] have been fabricated on GaAs and Si substrates using linearly graded buffers. Yang et al [117] compared the thermal resistances of InP-based HBTs on GaAs substrates using In x Al 1Àx As and In x Ga 1Àx P graded buffers by an experimental and modeling study.…”

Toward Ga‐Free Wavelength Extended 2.6 µm InAsP Photodetectors with High Performance

“…However, the high surface roughness (≈4 nm) and threading dislocation density (≈10 6 cm −2 ) of mixed‐cation In x Ga 1‐ x As absorbers pose challenges. [ 10 ] As an alternative, mixed‐anion InAs y P 1‐ y absorbers have potential advantages owing to their relatively low surface roughness and threading dislocation density. Additionally, such absorbers offer widely tunable bandgaps covering the whole SWIR spectral range (1−3 µm).…”

Metamorphic InGaAs p-i-n Photodetectors with 1.75 μm Cut-Off Wavelength Grown on GaAs

“…However, with the introduction of N, the crystalline quality of the InGaNAs is hard to improve because of the non-radiative recombination center. Metamorphic epitaxy has emerged to enable the growth of high quality InGaAs-based optoelectronic devices such as high electron mobility transistors (HEMTs), [7] heterojunction bipolar transistors (HBTs), [8] lasers [9,10] and PDs [11] on GaAs substrates. The mismatched InGaAs layer can be grown on a GaAs substrate to take advantage of a well-established GaAs electronic device technology.…”