Strain- and kinetically induced suppression of phase separation in MBE-grown metastable and unstable GaInAsSb quaternary alloys for mid-infrared optoelectronics

Abstract

The authors have examined the dependence of phase separation in thick layers (1 μm) of molecular beam epitaxially grown, thermodynamically metastable Ga(0.25)In(0.75)As(0.22)Sb(0.78) and unstable Ga(0.50)In(0.50)As(0.44)Sb(0.56) alloys on growth kinetics and strain. For the metastable alloy, which emits at 2.8 μms, they found that phase separation does not occur for any growth temperature, and the alloy grows stoichiometrically, with step flow growth and with high optical output at around 400 °C and 440–480 °C. Moreover, optical quality is robust for alloys grown up to 30 times the critical thickness, with evidence of some improvement for compressive strain. Remarkably, no relaxation of layers occurs, as evidenced in atomic force microscopy or reciprocal space maps up to 12 times the critical thickness. The unstrained unstable alloy, which emits at 3.9 μms, can be grown with optimal optical output and a low degree of phase separation by limiting adatom diffusion length with lower temperature growth (400–440 °C) than metastable alloy. At 450 °C and hotter, severe spinoidal decomposition occurs; however, the authors show that compressive strain may be employed to dramatically suppress phase separation.

Mid-wave interband cascade infrared photodetectors based on GaInAsSb absorbers

“…The hole barrier is composed of digitally graded three InAs/Al(In)Sb quantum wells (QWs) with well layer thickness of 83, 72, and  65 A, respectively. The electron barrier is composed of digitally graded seven GaSb/AlSb QWs with well layer thickness of 10,12,15,19,25,36 and  53 A, respectively, which is significantly thicker than the electron barrier with fewer GaSb/AlSb QWs in our previous ICIPs [1,2] and should be sufficient to force electrons move towards the preferred direction.…”

“…Although the growth of quaternary GaInAsSb alloys is challenging, especially in immiscibility regions [10,11], they have been used in IR optoelectronic devices such as lasers [12,13], thermophotovoltaics [14,15], and IR photodetectors [16][17][18]. Nevertheless, to the best of our knowledge, GaInAsSb detectors have not been reported in MWIR wavelength region beyond 3 μm even though the growth of thick GaInAsSb layer had been demonstrated on GaSb substrates with substantial strain and improved material quality [13,19,20]. Also, until this work, there has not been any study reported with bulk GaInAsSb material in ICIPs.…”

Broadband 2.4μm superluminescent GaInAsSb/AlGaAsSb quantum well diodes for optical sensing of biomolecules

“…However, these materials have been used in a number of successful laser diodes, as well, though the degree of phase separation and relaxation was not examined in those cases [20,21]. It has been shown that metastable and unstable GaInAsSb quaternary alloys can be grown under nonequilibrium conditions in MBE by employing low growth temperatures to limit adatom diffusion, and strain to suppress phase separation and improve material quality [22,23]. Figure 2(a) shows an optical interferometric image (Wyko NT1100 optical profiling system, 2 nm vertical resolution) of the surface of a bare quantum well sample consisting of one 14 nm 20 nm −1 Ga 0.58 In 0.42 As 0.14 Sb 0.86 / Al 0.25 Ga 0.75 As 0.02 Sb 0.98 quantum well with 100 nm Al 0.50 Ga 0.50 As 0.04 Sb 0.96 clads plus a 5 nm GaSb cap grown at 450 C. The surface has a smooth surface with a low density of small defects.…”