Metamorphic growth for application in long-wavelength (1.3–1.55 µm) lasers and MODFET-type structures on GaAs substrates

Abstract

In the present work we report on the optimization of MBE growth conditions and design of metamorphic In(Al)(Ga)As/GaAs heterostructures. This results in a strong decrease in the density of threading dislocations in the upper (active) layers and the improvement of surface morphology. Room-temperature mobility in metamorphic modulation-doped InGaAs/InAlAs heterostructures was 8100 cm2 V−1 s−1, which is comparable to that of InP-based structures and noticeably superior to pseudomorphic GaAs-based structures. InAs quantum dots formed in a metamorphic InGaAs matrix on a GaAs substrate were used for lasers with promising characteristics (emitting wavelengths of 1.46 µm, with threshold current densities of 1.4 kA cm−2).

Photoelectric properties of the metamorphic InAs/InGaAs quantum dot structure at room temperature

“…[1][2][3] By growing InAs nanoislands on relaxed InGaAs metamorphic buffers (MBs), it is possible to: (i) redshift the emission of QDs into the telecom windows at 1.3 and 1.55 lm and (ii) engineer properties of interest, such as activation energies for confined carriers and band discontinuities between QDs and embedding InGaAs layers, by controlling MBs parameters rather than QD parameters. 4 The relevance of these nanostructures for applications has been demonstrated by the fabrication of novel devices such as metamorphic QD lasers [5][6][7] and metamorphic QD solar cells.…”

“…4 The relevance of these nanostructures for applications has been demonstrated by the fabrication of novel devices such as metamorphic QD lasers [5][6][7] and metamorphic QD solar cells. 8 While some works have discussed in depth the underlying physics of metamorphic QDs and their growth peculiarities, [2][3][4]9,10 relatively less attention has been devoted to their electrical properties. However, these are fundamental not only for the design and development of devices such as edge-emitting lasers but also of more innovative devices such as single photon sources.…”

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].…”

“…Lowtemperature growth decreases the surface roughness [35,51,100,106,131,132], and this is expected because the reduced surface mobility of adatoms would decrease surface roughening by either mechanism. This model predicts increased indium segregation and, therefore, surface roughness, with increasing thickness or grading coefficient.…”

“…Linearly graded metamorphic buffers have been the widely used in device applications, including HEMTs [18,21,23,105,106,109,110,118,123,129,131,134,135], metal oxide semiconductor high electron mobility transistors (MOS HEMTs) [136], heterojunction bipolar transistors (HBTs) [113,117,118,137], LEDs [31,123], laser diodes [26,81,103,106,122], photodiodes [18,80,108,138,139], and solar cells [119]. Recent work with metamorphic HEMTs has emphasized In x Ga 1Àx As/In y Al 1Ày As quantum wells grown on GaAs (001) substrates by MBE [18,21,23,35,103,118,123,129,131,135].…”