Deep-ultraviolet AlGaN laser diodes employing a low-resistivity n-type contact layer

We demonstrate deep-ultraviolet (UV) AlGaN laser diodes (LDs) employing a Si-doped compositionally graded AlGaN n-type contact layer. The introduction of this contact layer significantly improved the Ohmic contact properties even for high-Al-content AlGaN (Al > 80%), yielding a low specific contact resistivity of 8.1 × 10−5 Ω cm2, thereby reducing the operating voltage and enhancing electron injection in the LDs. As a result, the LDs exhibit lasing at 284.1 nm with a threshold current density of ∼13.5 kA/cm2, lower than that of reference LDs without the contact layer. In addition, the electroluminescence intensity is approximately five times higher than that of LDs without the contact layer at 500 mA. These results indicate that the n-type contact layer plays a key role in enhancing electron injection in deep-UV AlGaN LDs.