Cook rice according to package directions. Meanwhile, place chicken in medium bowl. Sprinkle with salt and pepper; toss lightly.
Spray large skillet with cooking spray; heat over medium-high heat. Add chicken; cook and stir 4 to 5 minutes or until no longer pink. Add broccoli; stir-fry 2 to 3 minutes or until hot.
Stir together broth, cornstarch and garlic powder in small bowl until well blended. Gradually add to chicken mixture; cook 3 to 4 minutes or until sauce thickens, stirring constantly. Stir in lemon juice. Serve over rice.