TABLE OF CONTENTS The most thoroughly developed III-V semiconductor for MIR lasers is based on the InAsSb/InAsSbP quaternary alloy grown on InAs substrate. This material system is a promising candidate because it can cover the 3- to 5- ?m region by adjusting its alloy composition. Additionally, the InAsSbP material system has a fairly large growth window. The state-of-the-art growth, characterization, and operating characteristics for interband lasers based on the InAsSbP material system are presented and reviewed throughout this section.
InAsSbP is a quaternary alloy comprised of InAs, InSb, and InP binary materials. The physical properties of these binaries are summarized in Table 7.16. InAsSbP has a very wide range of energy gap and lattice constant values. Two binary substrates can be matched with the quaternary alloy: InAs and GaSb. However, InAs substrates are preferred because they are less expensive and of higher quality than GaSb substrates. Furthermore, GaSb has a relatively large refractive index that will reduce the optical confinement of the laser structures.
| T (K) | InAs | InSb | InP | |
|---|---|---|---|---|
| Crystal structure | Cubic (ZnS) | Cubic (ZnS) | Cubic (ZnS) | |
| Lattice constant ( ) | 300 | 6.0584 | 6.4788 | 5.8688 |
| Energy gap (eV) | 300 | 0.36 | 0.18 | 1.35 |
| 0 | 0.41 | 0.36 | 1.42 | |
| Melting point (K) | 1,215 | 803 | 1335 | |
| Coefficient of thermal expansion (10 -6K -1) | 300 | 4.52 | 5.04 | 5.0 |
| m e*/ m 0 | 4 | 0.024 | 0.014 | 0.077 |
| m lh*/ m 0 | 4 | 0.025 | 0.018 | 0.12 |
| m |
