# High-Power, High-Efficiency GaSb-Based Laser with Compositionally Linearly Graded AlGaAsSb Layer
## 4 Conclusions  
In this article, we calculate the composition dependence on the AlGaAsSb lattice constant. Precise control of As incorporation is essential for GaSb-lattice-matched AlGaAsSb layer epitaxy. The linear relationship between the As BEP and As content implies a constant As stacking coefficient. The linear modulation of As and Al BEP via cell temperature and valve position ramping is demonstrated. Composition-graded AlGaAsSb layer epitaxy was implemented by adopting the BEP modulation technique, and AFM and HRXRD results suggest high-quality and GaSb-lattice-matching crystal epitaxy.  
InGaSb/AlGaAsSb diode lasers with a composition-graded AlGaAsSb layer inserted between an Al\({}_{0.25}\)Ga\({}_{0.75}\)As\({}_{0.02}\)Sb\({}_{0.98}\) waveguide layer and an Al\({}_{0.5}\)Ga\({}_{0.5}\)As\({}_{0.04}\)Sb\({}_{0.96}\) cladding layer exhibit high-power and high-efficiency performance. A low turn-on voltage of 0.65 V and a low series resistance of 0.144 \(\Omega\) were realized. A maximum output power of 1.8 W and maximum power conversion efficiency of 28% were realized at 8 A and 1.1 A, respectively. A high internal quantum efficiency of 83% and low internal loss of 3.9 cm\({}^{-1}\) were measured at a 40 \({}^{\circ}\)C operating temperature, and 67 K \(T_{0}\) and 224 K \(T_{1}\) were obtained near room temperature with a 100 us pulse duration and 100 Hz repetition rate. A 0.95 cm laser bar with the same epitaxial structure was prepared, and a high CW power of 18 W was obtained at 75 A.  
Figure 10: Characteristic temperature of laser with 3 mm long cavity in CW. Threshold current and slope efficiency are measured with 5 \({}^{\circ}\)C to 45 \({}^{\circ}\)C heatsink temperature to determine \(T_{0}\) and \(T_{1}\).  
**Author Contributions:** Conceptualization, Y.C. and C.Y.; data curation, Y.C.; funding acquisition, C.Y., H.N., Y.Z. ([PERSON]), C.T., D.W. and Z.N.; investigation, Y.C., T.W., H.Y., J.S. and X.S.; methodology, Y.C.; project administration, Y.Z. ([PERSON]) and Z.N.; supervision, Z.N.; writing--original draft, Y.C.; writing--review and editing, C.Y. and Y.X. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the project \"Announce the list and take charge\" of the Major Special Plan of Science and Technology in Shanxi Province under grant number 202201030201009, the National Natural Science Foundation of China under grant number 62204238, the Jincheng Key Research and Development Project under grant number 20210209, the Chinese Academy of Sciences and Changchun City Science and Technology Innovation Cooperation Project under grant number 21 SH06, the Key R&D Program of Shanxi Province under grant number 202102030201004, and the R&D Program of Guangdong Province under grant numbers 2020B0303020001 and 2018B030329001.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.  
**Conflicts of Interest:** The authors declare no conflict of interest.