The Impact of In-Situ SiN_x Passivation Layers Grown with Different Carrier Gases on the Structural and Electrical Performance of GaN-MISHEMTs

In-situ <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiN}_{\mathrm{x}}$</tex> is a highly promising dielectric and passivation layer for GaN high electron mobility transistors (HEMTs). In this work, the growth mechanisms and device performance of in-situ silicon nitride under three different carrier gases including <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}_{2}(\mathrm{N}_{2}-\text{SiN}_{\mathrm{x}}),\ \mathrm{H}_{2}(\mathrm{H}_{2}-\text{SiN}_{\mathrm{x}})$</tex> ’ and mixed <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}_{2}/\mathrm{H}_{2}$</tex> atmosphere <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{N}/\mathrm{H}-\text{SiN}_{\mathrm{x}})$</tex> are studied. It is found that under three different carrier gas conditions, the growth rate of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiN}_{\mathrm{x}}$</tex> was influenced by the forward inhibition of the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiH}_{4}+ \text{NH}_{3}$</tex> reaction by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{H}_{2}$</tex>, resulting in the order of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}_{2} &gt; \mathrm{N}/\mathrm{H} &gt; \mathrm{H}_{2}$</tex>. Besides, due to the uniform in-situ etching effect of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{H}_{2}$</tex> on AlGaN layer, the surface and interface quality of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiN}_{\mathrm{x}}$</tex> for the N/H and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{H}_{2}$</tex> conditions were superior to that of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}_{2}$</tex>. In addition, it is interesting to note that the dilution effect of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}_{2}$</tex> on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{H}_{2}$</tex> results in a milder etching of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{H}_{2}$</tex>. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiN}_{\mathrm{x}}/\text{AlGaN}/\text{GaN}$</tex> based metal-insulator-semiconductor (MIS) HEMT made from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}/\mathrm{H}-\text{SiN}_{\mathrm{x}}$</tex> exhibit superior voltage-capacitance (C-V) dispersion effects compared to those made from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{H}_{2}-\text{SiN}_{\mathrm{x}}$</tex> and an even better device stability under 30 ks OFF- and ON-state electrical stress can be observed in the HEMT passivated by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}/\mathrm{H}-\text{SiN}_{\mathrm{x}}$</tex>. This indicates that the HEMT with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}/\mathrm{H}-\text{SiN}_{\mathrm{x}}$</tex> passivation has a lower density of interface states and defects. These results not only provide a detailed explanation of the in-situ growth mechanisms of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiN}_{\mathrm{x}}$</tex> under different carrier gases but also highlight the advancements made by using mixed <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}_{2}/\mathrm{H}_{2}$</tex> atmosphere as the carrier gas for in-situ <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiN}_{\mathrm{x}}$</tex> growth. This offers an effective strategy for customizing passivation schemes for GaN-based devices.