Progress on GaInAsSb And InAsSbP Photodetectors for MiD-Infrared Wavelengths
- PDF / 1,305,743 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 95 Downloads / 175 Views
still providing lattice-matched growth to the substrate material. Another expected advantage is that this detector structure will have good detectivity at room temperature, while most commercially available detectors need cooling to liquid nitrogen temperatures. Photodetectors operating in the mid-IR range will have a variety of commercial applications in air pollution monitoring, industrial process control, automobile emission monitoring, and future lightwave communication systems using novel fiber materials. EPITAXIAL GROWTH AND DEVICE FABRICATION Device layers of GaInAsSb, InAsSbP, and AlGaAsSb were grown by liquid phase epitaxy (LPE) to fabricate devices. A standard sliding graphite boat system was used. The different detector structures are detailed in the next section. Several solid-compositions for these detector materials were explored. The compositions used in this work and their growth parameters are given in Table I. The GaInAsSb and AIGaAsSb layers were grown on 500 ltm thick, chemically polished, (100) oriented, n-type GaSb wafers doped to 3-5 x 1017 cm 3 with tellurium, while the InAsSbP layers were grown on 500 itm thick, chemically polished, (100) oriented, n-type InAs wafers doped to 2-3 x 1018 cm"3 with sulfur. InAsSbP layers were also grown on GaSb substrates, but dissolution of the substrate caused poor quality layers not suitable for device fabrication. Starting melt compositions and temperatures for the growth of the epitaxial layers were determined from published liquidus phase equilibria data 79 and experimentation. The metal 135 Mat. Res. Soc. Symp. Proc. Vol. 484 ©1998 Materials Research Society
components of the melt were added as high purity (99.9999%) gallium, indium, and antimony shot pieces and aluminum wire. The arsenic was added as either undoped GaAs or InAs polycrystalline material. Phosphorous was added as undoped InP polycrystalline material. Prior to growth, the metal components of the melts were heated to 700 'C for fifteen hours under flowing hydrogen to de-oxidize the metallic melt components and outgas residual impurities. After cooling the melt 7 to 15 'C below the equilibrium temperature, the substrate was contacted with the melts at a cooling rate of 1 °C/min. to grow the device layers. Growth rates were typically 2-3 jtm/nmin. Table I. Growth parameters for epitaxial layers. solid composition liquid composition growth bandgap (eV) temp (°C) xLIn 0.59
xL
XLAs 0.01
XLsb 0.21
515
0.53
0.589
0.00088
0.01
0.40
565
0.44
0.001
0.028
515
1.10
XLAIl XLQ Gao.851no. 15Aso
17
0.19
Sbo 8 3
InAso.61Sbo.18Po.21
Alo28Gao 72Aso0 15Sbo9 85
0.015
0.957
The compositions of the epitaxial layers given in Table I were determined by electron microprobe analysis using wavelength dispersive spectroscopy (WDS). The compositions are very close to what was expected except for the InAsSbP which had a higher As concentration than expected. This may be due to the layer being so thin that the electron beam penetrated into the InAs substrate skewing the measurement towards higher
Data Loading...
