This is easier than you think and can be a case of mind over bunker !!!
The main thing that creates height in a bunker shot is wrist break on your backswing and acceleration through the sand.
The wrist break forces the club down to the bottom of the ball allowing the clubface to do the work and lift the ball for you.
As soon as you try and lift the ball yourself, (ie scoop the ball up) you will struggle with the height, in other words the more you try and lift the ball the lower it will go, hit DOWN and the ball will go up.
If you scoop the clubhead you will either take too much sand, hit too far before the ball, or hit the ball first and send it way over the green.
An even easier option to get extra height is to use a lob wedge.
The lob wedge has between 58 and 60 degrees of loft and hits the ball higher than your sand wedge.
Its also good for those shots where the pin is close to the front of the green or you have an extremely high lip on the bunker.
The main thing to remember in the bunker is to let the club do the work, hit down into the sand before the ball and follow right through with out scooping.